U.S. patent application number 09/862615 was filed with the patent office on 2001-10-18 for method for producing pyridine derivatives.
This patent application is currently assigned to KURARAY CO., LTD.. Invention is credited to Asanuma, Goro, Kikuyama, Shigeki, Matsuda, Hideki, Shin, Takanobu, Shiono, Manzo.
Application Number | 20010031871 09/862615 |
Document ID | / |
Family ID | 27298596 |
Filed Date | 2001-10-18 |
United States Patent
Application |
20010031871 |
Kind Code |
A1 |
Matsuda, Hideki ; et
al. |
October 18, 2001 |
Method for producing pyridine derivatives
Abstract
A pyridine alcohol derivative represented by General Formula III
1 (where A represents a divalent organic group which may contain
one to three oxygen atoms, nitrogen atoms and/or sulfur atoms,
wherein A may form a 5-, 6-, 7-, or 8-membered ring together with
two bonded carbon atoms, where said ring may form a condensed ring
with one or more additional rings; R.sup.5 represents a hydrogen
atom, --CHR.sup.1R.sup.2, or an alkenyl group, an aryl group or an
aralkyl group which may be substituted; R.sup.1 and R.sup.2 each
independently represent a hydrogen atom or a hydrocarbon group
which may be substituted; and R.sup.6 represents a hydrogen atom,
an alkyl group, an alkenyl group, an aryl group or an aralkyl group
which may be substituted), is produced by: reacting a pyridine
ester derivative represented by General Formula I-1 2 (where
Z.sup.1 represents --COX; X represents an alkoxyl group, an
alkenyloxy group, an aryloxy group or an aralkyloxy group which may
be substituted; and A is the same as above) with-a reducing agent,
an alkylating agent, an alkenylating agent, an arylating agent or
an aralkylating agent to obtain a pyridine carbonyl derivative
represented by General Formula II 3 (where A and R are the same as
above); and reacting the resulting pyridine carbonyl derivative
with a reducing agent, an alkylating agent, an alkenylating agent,
an arylating agent or an aralkylating agent to obtain the pyridine
alcohol derivative of the General Formula III.
Inventors: |
Matsuda, Hideki; (Okayama,
JP) ; Asanuma, Goro; (Okayama, JP) ; Shin,
Takanobu; (Okayama, JP) ; Shiono, Manzo;
(Okayama, JP) ; Kikuyama, Shigeki; (Okayama,
JP) |
Correspondence
Address: |
OBLON SPIVAK MCCLELLAND MAIER & NEUSTADT PC
FOURTH FLOOR
1755 JEFFERSON DAVIS HIGHWAY
ARLINGTON
VA
22202
US
|
Assignee: |
KURARAY CO., LTD.
1621, Sakazu, kurashiki-shi
Okayama
JP
710-8622
|
Family ID: |
27298596 |
Appl. No.: |
09/862615 |
Filed: |
May 23, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09862615 |
May 23, 2001 |
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09527916 |
Mar 17, 2000 |
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6265580 |
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09527916 |
Mar 17, 2000 |
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09175958 |
Oct 21, 1998 |
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6111111 |
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Current U.S.
Class: |
546/114 ;
540/552; 540/586; 540/593; 544/105; 544/279; 544/350; 544/48;
546/115; 546/122; 546/139 |
Current CPC
Class: |
C07D 491/04
20130101 |
Class at
Publication: |
546/114 ;
546/115; 546/122; 546/139; 544/279; 544/350; 544/105; 544/48;
540/552; 540/586; 540/593 |
International
Class: |
C07D 513/04; C07D
265/36 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 23, 1997 |
JP |
9-291075 |
Mar 16, 1998 |
JP |
10-64862 |
Aug 4, 1998 |
JP |
10-219943 |
Claims
What is claimed is:
1. A method for producing a pyridine alcohol derivative represented
by General Formula III 17(where A represents a divalent organic
group which may contain one to three oxygen atoms, nitrogen atoms
and/or sulfur atoms, wherein A may form a 5-, 6-, 7-, or 8-membered
ring together with two bonded carbon atoms, and said ring may form
a condensed ring with one or more additional rings; R.sup.5
represents a hydrogen atom, --CHR.sup.1R.sup.2, or an alkenyl
group, an aryl group or an aralkyl group which may be substituted;
R.sup.1 and R.sup.2 each independently represent a hydrogen atom or
a hydrocarbon group which may be substituted; and R.sup.6
represents a hydrogen atom, an alkyl group, an alkenyl group, an
aryl group or an aralkyl group which may be substituted), wherein
said method comprises: reacting a pyridine ester derivative
represented by General Formula I-1 18(where Z.sup.1 represents
--COX; X represents an alkoxyl group, an alkenyloxy group, an
aryloxy group or an aralkyloxy group which may be substituted; and
A is the same as above) with a reducing agent, an alkylating agent,
an alkenylating agent, an arylating agent or an aralkylating agent
to obtain a pyridine carbonyl derivative represented by General
Formula II 19(where A and R.sup.5 are the same as above); and
reacting the resulting pyridine carbonyl derivative represented by
General Formula II with a reducing agent, an alkylating agent, an
alkenylating agent, an arylating agent or an aralkylating agent to
obtain the pyridine alcohol derivative of the General Formula
III.
2. A method for producing a pyridine alcohol derivative represented
by General Formula III 20(where A represents a divalent organic
group which may contain one to three oxygen atoms, nitrogen atoms
and/or sulfur atoms, wherein A may form a 5-, 6-, 7-, or 8-membered
ring together with two bonded carbon atoms, and said ring may form
a condensed ring with one or more additional rings; R.sup.5
represents a hydrogen atom, --CHR.sup.1R.sup.2, or an alkenyl
group, an aryl group or an aralkyl group which may be substituted;
R.sup.1 and R.sup.2 each independently represent a hydrogen atom or
a hydrocarbon group which may be substituted; and R.sup.6
represents a hydrogen atom, an alkyl group, an alkenyl group, an
aryl group or an aralkyl group which may be substituted), wherein
said method comprises: reacting a pyridine carbonyl derivative
represented by General Formula II 21(where A and R.sup.5 are the
same as above) with a reducing agent, an alkylating agent, an
alkenylating agent, an arylating agent or an aralkylating agent to
obtain the pyridine alcohol derivative of the General Formula
III.
3. A pyridine carbonyl derivative represented by General Formula
II-1 22(where R represents a hydrogen atom, --CHR.sup.1R.sup.2, or
an alkenyl group, an aryl group or an aralkyl group which may be
substituted; R.sup.1 and R.sup.2 each independently represent a
hydrogen atom or a hydrocarbon group which may be substituted; Q
represents a divalent group selected from --ND--, --O--, and --S--;
and D represents a hydrogen atom or a hydrocarbon group which may
be substituted).
4. A method for producing a pyridine carbonyl derivative
represented by General Formula II 23(where A represents a divalent
organic group which may contain one to three oxygen atoms, nitrogen
atoms and/or sulfur atoms, wherein A may form a 5-, 6-, 7-, or
8-membered ring together with two bonded carbon atoms, and said
ring may form a condensed ring with one or more additional rings; R
represents a hydrogen atom, --CHR.sup.1R.sup.2, or an alkenyl
group, an aryl group or an aralkyl group which may be substituted;
and R.sup.1 and R.sup.2 each independently represent a hydrogen
atom, a hydrocarbon group which may be substituted), wherein said
method comprises: reacting a pyridine ester derivative represented
by General Formula I-1 24(where Z.sup.1 represents --COX; X
represents an alkoxyl group, an alkenyloxy group, an aryloxy group
or an aralkyloxy group which may be substituted; and A is the same
as above) with a reducing agent, an alkylating agent, an
alkenylating agent, an arylating agent or an aralkylating
agent.
5. A method for producing a pyridine alcohol derivative represented
by General Formula III 25(where A represents a divalent organic
group which may contain one to three oxygen atoms, nitrogen atoms
and/or sulfur atoms, wherein A may form a 5-, 6-, 7-, or 8-membered
ring together with two bonded carbon atoms, and said ring may form
a condensed ring with one or more additional rings; R.sup.5
represents a hydrogen atom, --CHR.sup.1R.sup.2, or an alkenyl
group, an aryl group or an aralkyl group which may be substituted;
R.sup.1 and R.sup.2 each independently represent a hydrogen atom or
a hydrocarbon group which may be substituted; and R.sup.6
represents a hydrogen atom, an alkyl group, an alkenyl group, an
aryl group or an aralkyl group which may be substituted), wherein
said method comprises: reacting a pyridine ester derivative
represented by General Formula I-1 26(where Z.sup.1 represents
--COX; X represents an alkoxyl group, an alkenyloxy group, an
aryloxy group or an aralkyloxy group which may be substituted; and
A is the same as above) in the presence of a base with an ester
compound represented by General Formula IV
R.sup.1R.sup.2CHCO.sub.2R.sup.3 (IV) (where R and R are the same as
above; and R represents a hydrocarbon group which may be
substituted) to obtain a pyridine .beta.-ketoester derivative
represented by General Formula V 27(where R.sup.1, R.sup.2, and A
are the same as above; and R.sup.4 is a hydrocarbon group which may
be substituted); and hydrolyzing and decarboxylating the resulting
pyridine .beta.-ketoester derivative represented by General Formula
V to obtain a pyridine carbonyl derivative represented by General
Formula II 28(where A and R.sup.5 are the same as above); and
reacting the pyridine carbonyl derivative represented by General
Formula II with a reducing agent, an alkylating agent, an
alkenylating agent, an arylating agent or an aralkylating agent to
obtain the pyridine alcohol derivative represented by General
Formula,III.
6. A method for producing a pyridine .beta.-ketoester derivative
represented by General Formula V 29(where R.sup.1 and R.sup.2 each
independently represent a hydrogen atom or a hydrocarbon group
which may be substituted; A represents a divalent organic group
which may contain one to three oxygen atoms, nitrogen atoms and/or
sulfur atoms, wherein A may form a 5-, 6-, 7-, or 8-membered ring
together with two bonded carbon atoms, and said ring may form a
condensed ring with one or more additional rings; and R.sup.4
represents a hydrocarbon group which may be substituted), wherein
said method comprises: reacting a pyridine ester derivative
represented by General Formula I-1 30(where Z.sup.1 represents
--COX; X represents an alkoxyl group, an alkenyloxy group, an
aryloxy group or an aralkyloxy group which may be substituted; and
A is the same as above) in the presence of a base with an ester
compound represented by General Formula IV
R.sup.1R.sup.2CHCO.sub.2R.sup.3 (IV) (where R.sup.1 and R.sup.2 are
the same as above; and R.sup.3 represents a hydrocarbon group which
may be substituted) to obtain the pyridine .beta.-ketoester
derivative represented by General Formula V.
7. A pyridine .beta.-ketoester derivative represented by General
Formula V-1 31(where R.sup.1 and R.sup.2 each independently
represent a hydrogen atom or a hydrocarbon group which may be
substituted; R.sup.4 represents a hydrocarbon group which may be
substituted; represents a divalent group selected from --ND--,
--O--, and --S--; and D represents a hydrogen atom or a hydrocarbon
group which may be substituted).
8. A method for producing a pyridine carbonyl derivative
represented by General Formula II 32(where A represents a divalent
organic group which may contain one to three oxygen atoms, nitrogen
atoms and/or sulfur atoms, wherein A may form a 5-, 6-, 7-, or
8-membered ring together with two bonded carbon atoms, and said
ring may form a condensed ring with one or more additional rings;
R.sup.5 represents a hydrogen atom, --CHR.sup.1R.sup.2, or an
alkenyl group, an aryl group or an aralkyl group which may be
substituted; and R.sup.1 and R.sup.2 each independently represent a
hydrogen atom or a hydrocarbon group which may be substituted),
wherein said method comprises: hydrolyzing and decarboxylating a
pyridine .beta.-ketoester derivative represented by General Formula
V 33(where R.sup.1, R.sup.2, and A are the same as above; and
R.sup.4 represents a hydrocarbon group which may be substituted) to
obtain the pyridine carbonyl derivative represented by General
Formula II.
9. A pyridine ester derivative represented by General Formula I-1'
34(where Z.sup.1 represents --COX; and X represents an alkoxyl
group, an alkenyloxy group, an aryloxy group or an aralkyloxy group
which may be substituted).
10. A sulfonylpyridine derivative represented by General Formula
I-2 35(where Z.sup.2 represents an organic sulfonyl group
represented by --SO.sub.2R.sup.9; R.sup.9 represents an organic
group; and A represents a divalent organic group which may contain
one to three oxygen atoms, nitrogen atoms and/or sulfur atoms,
wherein A may form a 5-, 6-, 7-, or 8-membered ring together with
two bonded carbon atoms, and said ring may form a condensed ring
with one or more additional rings).
11. A method for producing a pyridine derivative represented by
General Formula I 36(where n of Z.sup.n is 1 or 2; Z.sup.1
represents --COX; X represents an alkoxyl group, an alkenyloxy
group, an aryloxy group or an aralkyloxy group which may be
substituted; Z.sup.2 represents an organic sulfonyl group
represented by the formula, --SO.sub.2R.sup.9; R.sup.9 is an
organic group; and A represents a divalent organic group which may
contain one to three oxygen atoms, nitrogen atoms and/or sulfur
atoms, wherein A may form a 5-, 6-, 7-, or 8-membered ring together
with two bonded carbon atoms, where said ring may form a condensed
ring with one or more additional rings), wherein the method
comprises: reacting an imine derivative represented by General
Formula VI 37(where R is an alkyl group, an alkenyl group, an aryl
group or an aralkyl group which may be substituted; and A is the
same as above) with a carbonylating agent represented by General
Formula VII 38(where R.sup.8 is a hydrogen atom, or an alkyl group,
an alkenyl group, an aryl group, an aralkyl group, an alkoxyl
group, an alkenyloxy group, an aryloxy group, an aralkyloxy group
or an amino group which may be substituted; and Y represents a
leaving group) and a nitrile derivative represented by General
Formula VIII Z.sup.nCN (VIII) (where Zn is the same as above) to
obtain the pyridine derivative represented by General Formula I
12. A method according to claim 11, wherein a method for producing
an imine derivative represented by General Formula VI 39(where
R.sup.7 is an alkyl group, an alkenyl group, an aryl group or an
aralkyl group which may be substituted; and A represents a divalent
organic group which may contain one to three oxygen atoms, nitrogen
atoms and/or sulfur atoms, wherein A may form a 5-, 6-, 7-, or
8-membered ring together with two bonded carbon atoms, where said
ring may form a condensed ring with one or more additional rings),
wherein said method comprises: reacting an aldehyde derivative
represented by the General Formula IX 40(where A is the same as
above) with a primary amine represented by the General Formula X
R.sup.7NH.sub.2 (X) (where R.sup.7 is the same as above) to obtain
the imine derivative represented by General Formula VI.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to methods for producing
pyridine derivatives, and to intermediates in the synthesis
thereof. The pyridine derivatives produced by the present invention
are useful as intermediates in the synthesis of compounds having a
pyridine skeleton in the molecule, such as furopyridine derivatives
having antiviral activity (see WO 96/35678).
[0003] 2. Description of the Related Art
[0004] Several methods have been disclosed in the past as methods
for the synthesis of condensed pyridines such as furopyridines (see
Heterocycles, 45(5) (1997), p. 975), but the only known methods for
producing 5-substituted furo[2,3-c]pyridines which can be converted
to the aforementioned furopyridine derivatives having antiviral
activity are methods in which synthesis is achieved through
multiple stages using 2-chloro-3-hydroxypyridine as the starting
material (see WO 96/35678), and methods in which furfural oxime as
the starting material is made into 5-substituted
furo[2,3-c]pyridine-N-oxide as a result of ring formation by the
Aza Diels-Alder reaction and subsequent dehydrogenation (see
Tetrahedron Lett., 32, 3199(1991)).
[0005] Problems in the former of the aforementioned methods,
however, are the large number of steps as well as the expensive
starting materials and reaction agents, while the latter method
needs expensive dehydrogenating agents such as
2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), and needs the
reduction of the pyridine oxide to pyridine, and hence both methods
cannot be considered to be industrially useful.
SUMMARY OF THE INVENTION
[0006] An object of the present invention is to provide methods in
which pyridine derivatives, that allow condensed pyridines such as
furopyridine derivatives to be readily produced, can be
manufactured with good yields in an industrially useful manner
under moderate conditions.
[0007] Another object of the present invention is to provide a
synthetic intermediate and its method of production giving an
industrially useful method for producing the aforementioned
pyridine derivatives.
[0008] The aforementioned objects have been achieved in the
following present invention.
[0009] The present invention provides a method for producing a
pyridine alcohol derivative represented by General Formula III
4
[0010] (where A represents a divalent organic group which may
contain one to three oxygen atoms, nitrogen atoms and/or sulfur
atoms, wherein A may form a 5-, 6-, 7-, or 8-membered ring together
with two bonded carbon atoms, and said ring may form a condensed
ring with one or more additional rings; R.sup.5 represents a
hydrogen atom, --CHR.sup.1R.sup.2, or an alkenyl group, an aryl
group or an aralkyl group which may be substituted; R.sup.1 and
R.sup.2 each independently represent a hydrogen atom or a
hydrocarbon group which may be substituted; and R.sup.6 represents
a hydrogen atom, an alkyl group, an alkenyl group, an aryl group or
an aralkyl group which may be substituted), wherein the method
comprises:
[0011] reacting a pyridine ester derivative represented by General
Formula I-1 5
[0012] (where Z.sup.1 represents --COX; X represents an alkoxyl
group, an alkenyloxy group, an aryloxy group or an aralkyloxy group
which may be substituted; and A is the same as above)
[0013] with a reducing agent, an alkylating agent, an alkenylating
agent, an arylatihg agent or an aralkylating agent to obtain a
pyridine carbonyl derivative represented by General Formula II
6
[0014] (where A and R.sup.5 are the same as above); and
[0015] reacting the resulting pyridine carbonyl derivative
represented by General Formula II with a reducing agent, an
alkylating agent, an alkenylating agent, an arylating agent or an
aralkylating agent to obtain the pyridine alcohol derivative of the
General Formula III.
[0016] The present invention also provides a method for producing a
pyridine alcohol derivative represented by General Formula III,
wherein the method comprises:
[0017] reacting a pyridine carbonyl derivative represented by
General Formula II with a reducing agent, an alkylating agent, an
alkenylating agent, an arylating agent or an aralkylating agent to
obtain the pyridine alcohol derivative of the General Formula
III.
[0018] The present invention further provides a pyridine carbonyl
derivative represented by General Formula II-1 7
[0019] (where R represents a hydrogen atom, --CHR.sup.1R.sup.2, or
an alkenyl group, an aryl group or an aralkyl group which may be
substituted; R.sup.1 and R.sup.2 each independently represent a
hydrogen atom or a hydrocarbon group which may be substituted; Q
represents a divalent group selected from --ND--, --O--, and --S--;
and D represents a hydrogen atom or a hydrocarbon group which may
be substituted).
[0020] The present invention still further provides a method for
producing a pyridine carbonyl derivative represented by General
Formula II, wherein the method comprises:
[0021] reacting a pyridine ester derivative represented by General
Formula I-1 with a reducing agent, an alkylating agent, an
alkenylating agent, an arylating agent or an aralkylating
agent.
[0022] The present invention also provides a method for producing a
pyridine alcohol derivative represented by General Formula III,
wherein the method comprises:
[0023] reacting a pyridine ester derivative represented by General
Formula I-1 in the presence of a base with an ester compound
represented by General Formula IV
R.sup.1R.sup.2CHO.sub.2R.sup.3 (IV)
[0024] (where R.sup.1 and R.sup.2 are the same as above; and
R.sup.3 represents a hydrocarbon group which may be substituted) to
obtain a pyridine .beta.-ketoester derivative represented by
General Formula V 8
[0025] (where R.sup.1, R.sup.2, and A are the same as above; and
R.sup.4 is a hydrocarbon group which may be substituted); and
[0026] hydrolyzing and decarboxylating the resulting pyridine
.beta.-ketoester derivative represented by General Formula V to
obtain the pyridine carbonyl derivative represented by General
Formula II; and
[0027] reacting the pyridine carbonyl derivative represented by
General Formula II with a reducing agent, an alkylating agent, an
alkenylating agent, an arylating agent or an aralkylating agent to
obtain the pyridine alcohol derivative represented by General
Formula III.
[0028] The present invention further provides a method for
producing a pyridine .beta.-ketoester derivative represented by
General Formula V, wherein the method comprises:
[0029] reacting a pyridine ester derivative represented by General
Formula I-1 with in the presence of a base with an ester compound
represented by General Formula IV to obtain the pyridine
.beta.-ketoester derivative represented by General Formula V.
[0030] The present invention still further provides a pyridine
.beta.-ketoester derivative represented by General Formula V-1
9
[0031] (where R.sup.1 and R.sup.2 each independently represent a
hydrogen atom or a hydrocarbon group which may be substituted;
R.sup.4 represents a hydrocarbon group which may be substituted; Q
represents a divalent group selected from --ND--, --O--, and --S--;
and D represents a hydrogen atom or a hydrocarbon group which may
be substituted).
[0032] The present invention also provides a method for producing a
pyridine carbonyl derivative represented by General Formula II,
wherein the method comprises:
[0033] hydrolyzing and decarboxylating a pyridine .beta.-ketoester
derivative represented by General Formula V to obtain the pyridine
carbonyl derivative represented by General Formula II.
[0034] The present invention also provides a pyridine ester
derivative represented by General Formula I-1' 10
[0035] (where Z.sup.1 represents --COX; and X represents an alkoxyl
group, alkenyloxy group, aryloxy group or aralkyloxy group which
may be substituted).
[0036] The present invention also provides a sulfonylpyridine
derivative represented by General Formula I-2 11
[0037] (where Z represents an organic sulfonyl group represented by
--SO.sub.2R.sup.9; R.sup.9 represents an organic group; and A
represents a divalent organic group which may contain one to three
oxygen atoms, nitrogen atoms and/or sulfur atoms, wherein A may
form a 5-, 6-, 7-, or 8-membered ring together with two bonded
carbon atoms, and said ring may form a condensed ring with one or
more additional rings).
[0038] The present invention also provides a method for producing a
pyridine derivative represented by General Formula I 12
[0039] (where n of z is 1 or 2; Z.sup.1 represents --COX; X
represents an alkoxyl group, an alkenyloxy group, an aryloxy group
or an aralkyloxy group which may be substituted; Z.sup.2 represents
an organic sulfonyl group represented by the formula,
--SO.sub.2R.sup.9; R.sup.9 is an organic group; and A represents a
divalent organic group which may contain one to three oxygen atoms,
nitrogen atoms and/or sulfur atoms, wherein A may and form a 5-,
6-, 7-, or 8-membered ring together with two bonded carbon atoms,
and said ring may form a condensed ring with one or more additional
rings), wherein the method comprises:
[0040] reacting an imine derivative represented by General Formula
VI 13
[0041] (where R.sup.7 is an alkyl group, an alkenyl group, an aryl
group or an aralkyl group which may be substituted; and A is the
same as above)
[0042] with a carbonylating agent represented by General Formula
VII 14
[0043] (where R.sup.8 is a hydrogen atom, an alkyl group, an
alkenyl group, an aryl group, an aralkyl group, an alkoxyl group,
an alkenyloxy group, an aryloxy group, an aralkyloxy group or an
amino group which may be substituted; and Y represents a leaving
group)
[0044] and a nitrile derivative represented by General Formula
VIII
Z.sup.nCN (VIII)
[0045] (where Zn is the same as above)
[0046] to obtain the pyridine derivative represented by General
Formula I.
[0047] The imine derivative represented by General Formula VI may
preferably be obtainable by a method comprises:
[0048] reacting an aldehyde derivative represented by the General
Formula IX 15
[0049] (where A is the same as above)
[0050] with a primary amine represented by the General Formula
X
R.sup.7NH.sub.2 (X)
[0051] (where R.sup.7 is the same as above)
[0052] to obtain the imine derivative represented by General
Formula VI.
[0053] These and other objects, features and advantages of the
present invention are described in or will become apparent from the
following detailed description of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0054] The present invention will be explained in more detail by
referring to the following Reaction Scheme. 16
[0055] First, the substituents referred to in the General Formulas
in the Reaction Scheme are explained below.
[0056] Specific examples of rings formed by A together with two
bonded carbon atoms in the aforementioned general formula include
5-membered rings such as a dihydrofuran ring, a furan ring, a
pyrrole ring, a pyrroline ring, a dehydrodioxolane ring, a pyrazole
ring, a pyrazoline ring, an imidazole ring, an oxazole ring, an
isooxazole ring, a thiazole ring, an oxadiazole ring, and a
triazole ring; 6-membered rings such as a pyran ring, a
dihydropyran ring, a pyridine ring, a dihydropyridine ring , a
tetrahydropyridine ring, a dehydrodioxane ring, a dehydromorpholine
ring, a pyridazine ring, a dihydropyridazine ring, a pyrimidine
ring, a dihydropyrimidine ring, a tetrahydropyrimidine ring, a
pyrazine ring, and a dihydropyrazine ring; 7-membered rings such as
a thiazepine ring and various aza, oxa and thia substituted
derivatives of a cycloheptene ring, a cycloheptadiene ring and a
cycloheptatriene ring; and 8-membered rings such as various aza,
oxa or thia substituted derivatives of a cyclooctene ring, a
cyclooctadiene ring and a cyclooctatetraene ring.
[0057] Specific examples of condensed rings in cases where the ring
formed by A together with two bonded carbon atoms forms a condensed
ring with one or more other rings include a benzofuran ring, an
isobenzofuran ring, a chromene ring, an indolizine ring, an indole
ring, an isoindole ring, a quinolizine ring, an indazole ring, an
isoquinoline ring, a phthalazine ring, a naphthylizine ring, a
quinoxaline ring, a benzothiophene ring and their hydrogenated
forms. Any of the above rings may be substituted.
[0058] Examples of alkoxyl groups represented by X or R.sup.8
include linear or branched alkoxyl groups such as methoxy, ethoxy,
propoxy, isopropoxy, butoxy, hexyloxy and octyloxy; and
cycloalkyloxy groups such as cyclopropyloxy, cyclopentyloxy, and
cyclohexyloxy. These alkoxyl groups and cycloalkyloxy groups may be
substituted, where examples of such substituents include halogen
atoms such as chlorine, bromine, iodine and fluorine; alkoxyl
groups such as methoxy, ethoxy, propoxy and butoxy; hydroxyl group;
nitro group; and aryl groups such as phenyl, p-methoxyphenyl and
p-chlorophenyl.
[0059] Examples of alkenyloxy groups represented by X or R.sup.8
include propenyloxy, butenyloxy and octenyloxy; examples of aryloxy
groups include the phenyloxy; and examples of aralkyloxy groups
include the benzyloxy. These alkenyloxy, aryloxy and aralkyloxy
groups may be substituted, where examples of such substituents
include halogen atoms such as chlorine, bromine, iodine and
fluorine; alkoxyl groups such as methoxy, ethoxy, propoxy and
butoxy; hydroxyl group; alkyl groups such as methyl, ethyl, propyl
and butyl; tri-substituted silyloxy groups such as
tert-butyldimethylsilyloxy and tert-butyldiphenylsilyloxy; nitro
group; and aryl groups such as phenyl, p-methoxyphenyl and
p-chlorophenyl.
[0060] Examples of organic groups represented by R.sup.9 include
alkyl groups such as methyl, ethyl, propyl, ter-butyl, octyl and
dodecyl; aryl groups such as phenyl, tolyl, chlorophenyl,
nitrophenyl and naphthyl; and aralkyl groups such as benzyl and
nitrobenzyl.
[0061] Examples of hydrocarbon groups represented by R.sup.1,
R.sup.2, R.sup.3, R.sup.4 and D include alkyl, alkenyl, aryl and
aralkyl groups. Examples of alkyl groups include linear or branched
alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl,
isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl,
hexyl, heptyl and octyl; and cycloalkyl groups such as cyclopropyl,
cyclopentyl and cyclohexyl. These alkyl groups may be substituted,
where examples of such substituents include halogen atoms such as
chlorine, bromine, iodine and fluorine; alkoxyl groups such as
methoxy, ethoxy, propoxy and butoxy; hydroxyl group;
tri-substituted silyloxy groups such as tert-butyldimethylsilyloxy
and tert-butyldiphenylsilyloxy; nitro group; and aryl groups such
as phenyl, p-methoxyphenyl and p-chlorophenyl.
[0062] Examples of alkenyl groups include vinyl, propenyl, butenyl
and octenyl; examples of aryl groups include phenyl; and examples
of aralkyl groups include benzyl. These alkenyl, aryl, and aralkyl
groups may be substituted, where examples of such substituents
include halogen atoms such as chlorine, bromine, iodine and
fluorine; alkoxyl groups such as methoxy, ethoxy, propoxy and
butoxy; hydroxyl group; alkyl groups such as methyl, ethyl, propyl
and butyl; tri-substituted silyloxy groups such as
tert-butyldimethylsilyloxy and tert-butyldiphenylsilyloxy; nitro
group; and aryl groups such as phenyl, p-methoxyphenyl and
p-chlorophenyl.
[0063] Examples of alkyl groups represented by R.sup.5, R.sup.6,
R.sup.7 and R.sup.8 include linear or branched alkyl groups such as
methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl,
tert-butyl, pentyl, isopentyl, neopentyl, hexyl, heptyl and octyl;
and cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl
and cyclohexyl.
[0064] These alkyl groups may be substituted, where examples of
such substituents include halogen atoms such as chlorine, bromine,
iodine and fluorine; hydroxyl group; alkoxyl groups such as
methoxy, ethoxy, propoxy and butoxy; tri-substituted silyloxy
groups such as tert-butyldimethylsilyloxy and
tert-butyldiphenylsilyloxy; nitro group; and aryl groups such as
phenyl, p-methoxyphenyl and p-chlorophenyl.
[0065] Examples of alkenyl groups represented by R.sup.5, R.sup.6,
R.sup.7 and R.sup.8 include vinyl, propenyl, butenyl and octenyl;
examples of aryl groups include phenyl and naphthyl; and examples
of aralkyl groups include benzyl. These alkenyl, aryl and aralkyl
groups may be substituted, where examples of such substituents
include halogen atoms such as chlorine, bromine, iodine and
fluorine; hydroxyl group; alkyl groups such as methyl, ethyl,
propyl and butyl; alkoxyl groups such as methoxy, ethoxy, propoxy
and butoxy; tri-substituted silyloxy groups such as
tert-butyldimethylsilyloxy and tert-butyldiphenylsilyloxy; nitro
group; and aryl groups such as phenyl, p-methoxyphenyl, and
p-chlorophenyl.
[0066] Examples of substitutable amino groups represented by
R.sup.8 include C1 to C8 linear or branched amino groups such as
amino, dimethylamino, diethylamino, dipropylamino,
diisopropylamino, dibutylamino, dihexylamino and dioctylamino.
[0067] These amino groups may be substituted by halogen atoms such
as chlorine, bromine, iodine or fluorine; hydroxyl group; alkoxyl
groups such as methoxy, ethoxy, propoxy or butoxy; tri-substituted
silyloxy groups such as tert-butyldimethylsilyloxy and
tert-butyldiphenylsilyloxy; nitro group; and phenyl,
p-methoxyphenyl and p-chlorophenyl groups.
[0068] Examples of leaving groups represented by Y include halogen
atoms such as chlorine, bromine and iodine, and acyloxy groups such
as acetoxy, propionyloxy, butyryloxy and valeryloxy.
[0069] Production method of the present invention is described in
each step in detail below.
[0070] Step (a): Step for producing an imine derivative VI by
subjecting an aldehyde derivative IX and a primary amine X to
dehydration condensation.
[0071] This conversion can be carried out in the same way as in
methods commonly used to obtain an imine compound from an aldehyde
and a primary amine. For example, the aldehyde derivative IX and
the primary amine X are mixed in the presence or absence of a
solvent and in the presence or absence of a dehydrating agent.
Suitable solvents are those which give no undesired effect on the
reaction, including aliphatic hydrocarbon solvents such as pentane,
hexane, heptane and ligroin; aromatic hydrocarbon solvents such as
benzene, toluene, xylene and chlorobenzene; ether solvents such as
diethyl ether, tetrahydrofuran and dioxane; alcohol solvents such
as methanol and ethanol; ester solvents such as methyl acetate,
ethyl acetate and butyl acetate; or a mixture thereof. Suitable
dehydrating agents include silica gel, molecular sieves, alumina,
sodium sulfate, magnesium sulfate, copper sulfate, sodium
hydroxide, or potassium hydroxide. The reaction can also be carried
out in an azeotropic solvent with water while removing water by
azeotropic dehydration.
[0072] Examples of the primary amines X include methylamine,
ethylamine, propylamine, n-buthylamine, n-hexylamine, n-octylamine,
aniline, p-chloroaniline, p-methoxyaniline, p-methylaniline and
p-nitroaniline.
[0073] The resulting imine derivative VI is isolated and purified
from the reaction mixture in the usual manner which commonly used
in the isolation and purification of organic compounds. For
example, the imine derivatives VI can be obtained by separating
insoluble material contained in the reaction mixture by filtration,
concentrating the filtrate and then purifing the residue by
recrystallization, chromatography, or the like. The crude product
can also be used without purification as such in subsequent
reactions. When the imine derivative VI is precipitated from the
reaction mixture, it is filtered, purified by recrystallization if
necessary, and then can be used in the subsequent reaction.
[0074] Step (b): Step for producing a pyridine derivative I by
reacting an imine derivative VI with a carbonylating agent VII and
a nitrile VIII.
[0075] Examples of carbonylating agents VII include carboxylic
anhydrides such as acetic anhydride, propionic anhydride, butyric
anhydride, valeric anhydride and trifluoroacetic anhydride;
carboxylic acid halides such as acetyl chloride, acetyl bromide,
propionyl chloride, propionyl bromide, butyryl chloride, isobutyryl
chloride, valeryl chloride, isovaleryl chloride, pivaloyl chloride,
benzoyl chloride and benzoyl bromide; halogenoformic acid esters
such as methyl chloroformate, ethyl chloroformate, propyl
chloroformate, isopropyl chloroformate, butyl chloroformate, allyl
chloroformate, phenyl chloroformate, nitrophenyl chloroformate and
benzyl chloroformate; and carbamic acid halides such as
N,N-dimethylcarbamyl chloride; among these chloroformic acid esters
are preferred.
[0076] The amount of carbonylating agent VII may be used within a
range of preferably 0.5 to 20 mol, and more preferably 1.1 to 10
mol, based on one mole of the imine derivative VI.
[0077] Examples of nitriles VIII include alkylsulfonylcyanides such
as methanesulfonylcyanide, ethanesulfonylcyanide,
propanesulfonylcyanide, butanesulfonylcyanide,
tert-butanesulfonylcyanide, and dodecanesulfonylcyanide;
arylsulfonylcyanides such as benzenesulfonylcyanide,
toluenesulfonylcyanide, chlorobenzenesulfonylcyan- ide,
nitrobenzenesulfonylcyanide and naphthalenesulfonylcyanide;
aralkylsulfonylcyanides such as benzylsulfonylcyanide and
nitrobenzylsulfonylcyanide; cyanoformic acid esters such as methyl
cyanoformate, ethyl cyanoformate, propyl cyanoformate, isopropyl
cyanoformate, butyl cyanoformate, allyl cyanoformate, phenyl
cyanoformate, nitrophenyl cyanoformate and benzyl cyanoformate. The
amount of nitrile VIII may be used within a range of preferably 0.5
to 20 mol, and more preferably 1.1 to 10 mol, based on one mole of
the imine derivative VI.
[0078] The reaction can be carried out in the presence or absence
of a solvent. The solvent is not particularly limited, provided
that the reaction is not adversely affected, examples of which
include aromatic hydrocarbons such as benzene, toluene, xylene,
mesitylene and chlorobenzene; ethers such as tetrahydrofuran and
dioxane; amides such as dimethyl formamide and
1-methyl-2-pyrrolidinone; and dimethyl sulfoxide. The amount of the
solvent is not particularly limited, although it is usually used
within a rage of preferably 1 to 200 times by weight based on the
imine derivative VI.
[0079] The reaction temperature may vary, depending on the solvent,
the carbonylating agent VII, and the nitrile VIII that is used, but
is preferably within a range of 40.degree. C. to the reflux
temperature of the reaction system. The reaction can be carried out
in a pressurized or reduced pressure state. The reaction time may
vary, depending on the reaction temperature, but is usually rages
from 30 minutes to 24 hours. The reaction time can be controlled by
properly controlling the reaction temperature.
[0080] The reaction is carried out in the following manner, for
example. That is, the carbonylating agent VII is added dropwise to
a mixed solution of the nitrile VIII and the imine derivative VI
within a temperature range from under ice cooling to the refluxing
temperature of the reaction mixture, and after the completion of
addition, the mixture is heated to the desired temperature until
the imine derivative VI disappears.
[0081] The resulting pyridine derivative I is isolated and purified
from the reaction mixture in the usual manner which commonly used
in the isolation and purification of organic compounds. For
example, after cooling the reaction mixture to room temperature, it
is washed with sodium bicarbonate aqueous solution and saline
water. Then, the solvent is distilled off, and the residue is
purified by recrystallization, chromatography, or the like. When
the product is precipitated from the reaction mixture, the reaction
mixture can be cooled and then filtered with the addition of a poor
solvent if necessary.
[0082] Step (c): Step for producing a pyridine carbonyl derivative
II by reacting a pyridine ester derivative I-1 with a reducing
agent, an alkylating agent, an alkenylating agent, an arylating
agent or an aralkylating agent.
[0083] Examples of reducing agents include metal borohydrides such
as sodium borohydride and lithium borohydride; and metal aluminum
hydrides such as diisobutyl aluminum hydride, lithium aluminum
hydride and sodium bismethoxyethoxyaluminum hydride. Examples of
alkylating agents include alkyl metal compounds such as
methyllithium, n-butyllithium, methylmagnesium chloride,
methylmagnesium bromide, ethylmagnesium chloride and methylcerium
chloride; examples of alkenylating agents include alkenyl metal
compounds such as vinyllithium, vinylmagnesium chloride,
allyllithium and allylmagnesium chloride; examples of arylating
agents include aryl metal compounds such as phenyllithium and
phenylmagnesium bromide; and examples of aralkylating agents
include aralkyl metal compounds such as benzyllithium and
benzylmagnesium bromide. The amount of reducing agent, the
alkylating agent, the alkenylating agent, the arylating agent or
the aralkylating agent may be used within a range of preferably 0.5
to 20 mol, and more preferably 1.1 to 2.0 mol, based on one mole of
the pyridine ester derivative I-1.
[0084] The reaction can be carried out in the presence or absence
of a solvent. The solvent is not particularly limited, provided
that the reaction is not adversely affected, examples of which
include ethers such as diethyl ether, diisopropyl ether, dibutyl
ether, tetrahydrofuran, 1,2-diethoxyethane and diethylene glycol
dimethyl ether; hydrocarbons such as hexane, benzene, toluene,
xylene, mesitylene, and chlorobenzene; and amides such as
1-methyl-2-pyrrolidinone. The amount of solvent is not particularly
limited, although it is usually used within a range of preferably 1
to 200 times by weight based on the pyridine ester derivative
I-1.
[0085] The reaction temperature may vary, depending on the solvent,
the reducing agent, the alkylating agent, the alkenylating agent,
the arylating agent or the aralkylating agent that is used, but a
temperature is usually preferred within a range of -100.degree. C.
to the refluxing temperature of the solvent. The reaction can be
carried out in a pressurized or reduced pressure state. The
reaction time also may vary, depending on the reaction temperature,
but is usually range from 30 minutes to 24 hours. The reaction time
can be controlled by properly controlling of the reaction
temperature.
[0086] The resulting pyridine carbonyl derivative II is isolated
and purified from the reaction mixture in the usual manner which
commonly used in the isolation and purification of organic
compounds. For example, after returning the reaction mixture to
room temperature, it is then added to an acidic aqueous solution
such as aqueous ammonium chloride and is hydrolyzed, it is then
extracted with an organic solvent such as diethyl ether or ethyl
acetate, the extract is washed with sodium bicarbonate aqueous
solution and saline water, the solvent is distilled off, and the
residue is purified by distillation, recrystallization,
chromatography, or the like.
[0087] A pyridine alcohol derivative III in which R.sup.5 and
R.sup.6 are a hydrogen atom can be obtained in a single stage when
using a reducing agent with hydrogen as a nucleophilic agent, metal
borohydrides such as sodium borohydride, lithium borohydride; and
metal aluminum hydrides such as lithium aluminum hydride, sodium
bismethoxyethoxyaluminum hydride.
[0088] Step (d): Step for producing a pyridine alcohol derivative
III by reacting a pyridine carbonyl derivative II with a reducing
agent, an alkylating agent, an alkenylating agent, an arylating
agent or an aralkylating agent.
[0089] Examples of reducing agents include metal borohydrides such
as sodium borohydride and lithium borohydride and metal aluminum
hydrides such as diisobutyl aluminum hydride, lithium aluminum
hydride, and sodium bismethoxyethoxyaluminum hydride. Reduction can
also be carried out the use of hydrogen in the presence of a metal
catalyst such as Raney nickel or Raney cobalt. Reduction by
aluminum isopropoxide in isopropanol can also be adopted. The
amount of the reducing agent may be used preferably within a range
of 1.0 to 20 mol, and preferably 1.1 to 5 mol, based on one mole of
the pyridine carbonyl derivative II.
[0090] Examples of alkylating agents include alkyl metal compounds
such as methyllithium, n-butyllithium, methylmagnesium chloride,
methylmagnesium bromide, ethylmagnesium chloride, and methylcerium
chloride; examples of alkenylating agents include alkenyl metal
compounds such as vinyllithium, vinylmagnesium chloride,
allyllithium, and allylmagnesium chloride; examples of arylating
agents include aryl metal compounds such as phenyllithium and
phenylmagnesium bromide; and examples of aralkylating agents
include aralkyl metal compounds such as benzyllithium and
benzylmagnesium bromide. The amount of alkylating agent, the
alkenylating agent, the arylating agent or the aralkylating agent
may be used within a range of preferably 0.5 to 20 mol, and more
preferably 1.1 to 2.0 mol, based on one mole of the pyridine
carbonyl derivative II.
[0091] The reaction can be carried out in the presence or absence
of a solvent. The solvent is not particularly limited, provided
that the reaction is not adversely affected, examples of which
include alcohols such as methanol, ethanol, propanol and
isopropanol; ethers such as diethyl ether, diisopropyl ether,
dibutyl ether, tetrahydrofuran, 1,2-diethoxyethane and diethylene
glycol dimethyl ether; and hydrocarbons such as hexane, heptane,
cyclohexane, benzene, toluene, and xylene. The amount of solvent is
not particularly limited, although it is preferably used within a
range of 1 to 200 times by weight based on the pyridine carbonyl
derivative II.
[0092] The reaction temperature may vary, depending on the solvent,
the reducing agent, the alkylating agent, the alkenylating agent,
the arylating agent or the aralkylating agent that is used, but a
temperature is preferred within a range of -100.degree. C. to the
refluxing temperature of the solvent. The reaction can be carried
out in a pressurized or reduced pressure state. The reaction time
also may vary, depending on the reaction temperature, but is
usually range from 30 minutes to 24 hours. The reaction time can be
controlled by properly controlling of the reaction temperature.
[0093] The resulting pyridine alcohol derivative III is isolated
and purified from the reaction mixture in the usual manner which
commonly used in the isolation and purification of organic
compounds. For example, after returning the reaction mixture to
room temperature, the reaction mixture is then added to an acidic
aqueous solution such as aqueous ammonium chloride and is
hydrolyzed, it is then extracted with an organic solvent such as
diethyl ether or ethyl acetate, the extract is washed with sodium
bicarbonate aqueous solution and saline water, the solvent is
distilled off, and the residue is purified by distillation,
recrystallization, chromatography, or the like.
[0094] Step (e): Step for producing a pyridine .beta.-ketoester
derivative V by reacting a pyridine ester derivative I-1 with an
ester compound IV in the presence of a base.
[0095] Examples of bases include alkali metals such as sodium,
lithium, and potassium; alkaline earth metals such as calcium;
metal alcoholates such as sodium methoxide, sodium ethoxide, sodium
propoxide, sodium isopropoxide, sodium butoxide, sodium
tert-butoxide, sodium benzyloxide, potassium methoxide, potassium
ethoxide, potassium propoxide, potassium isopropoxide, potassium
butoxide and potassium tert-butoxide; organic magnesium halides
such as methylmagnesium bromide, ethylmagnesium bromide,
isopropylmagnesium bromide, and mesitylmagnesium bromide; metal
hydrides such as sodium hydride and potassium hydride; and metal
amides such as sodium amide, potassium amide, and lithium
diisopropylamide. The amount of base is preferably used within a
range of 0.5 to 10 mol, and more preferably 1 to 3 mol, based on
one mole of the pyridine ester derivative I-1.
[0096] The ester compound IV is an ester compound derived from a
carboxylic acid having a hydrogen atom in the alpha position,
preferably an ester compound, such as a methyl ester, ethyl ester,
propyl ester, isopropyl ester, butyl ester, isobutyl ester,
2-methylpropyl ester, tert-butyl ester, phenyl ester, benzyl ester,
or chlorophenyl ester of a carboxylic acid such as acetic acid,
propionic acid, butyric acid, isobutyric acid, 2-methylpropionic
acid, valeric acid, isovaleric acid, caproic acid, or phenylacetic
acid. Among these, aliphatic lower alcohol esters such as methyl
esters, ethyl esters, propyl esters, isopropyl esters, butyl
esters, isobutyl esters, 2-methylpropyl esters and tert-butyl
esters are preferred.
[0097] The amount of ester compound IV is used preferably within a
range of 0.5 to 10 mol, and more preferably 1 to 3 mol, based on
one mole of the pyridine ester derivative I-1.
[0098] Although the reaction in this step can be carried out in the
absence of a solvent, it is preferably carried out in the presence
of a solvent.
[0099] Solvents are not particularly limited, provided that the
reaction is not adversely affected, examples of which include
aliphatic hydrocarbons such as pentane, hexane, cyclohexane, octane
and ligroin; aromatic hydrocarbons such as benzene, toluene,
xylene, cumene and mesitylene; ethers such as diethyl ether,
tetrahydrofuran, and dioxane; polyethers such as ethylene glycol
dimethyl ether, diethylene glycol dimethyl ether, triethylene
glycol dimethyl ether, tetraethylene glycol dimethyl ether,
ethylene glycol diethyl ether, diethylene glycol diethyl ether,
triethylene glycol diethyl ether and tetraethylene glycol diethyl
ether; and alcohols such as methanol, ethanol, propanol,
isopropanol, butanol and t-butanol. Among these, the use of
aromatic hydrocarbons, ethers, and polyethers as the solvent is
preferred in view of the reaction rate, solubility of the pyridine
derivative I, and the like. The amount of solvent is not
particularly limited, provided that it is an amount allowing the
pyridine ester derivative I-1 to dissolve under the reaction
conditions, although it is preferably used within a range of 0.5 to
1000 times by weight, and more preferably 0.5 to 100 times by
weight, based on the pyridine ester derivative I-1.
[0100] The reaction temperature is preferably within a range of 0
to 200.degree. C., and more preferably 10 to 150.degree. C.
[0101] The reaction in this step is not limited to any particular
method, examples of which include: (1) mixing the prescribed
amounts of the pyridine ester derivative I-1, the base, the ester
compound IV and a solvent, and allowing the mixture to react at the
prescribed temperature; (2) dissolving the prescribed amount of the
pyridine ester derivative I-1 in a solvent, adding the base to the
solution, heating the solution to the desired temperature, and then
adding the ester compound IV all at once, intermittently or
continuously, either as such or dissolved in a solvent; and (3)
dissolving the prescribed amount of the base in the solvent, adding
the ester compound IV to the solution, heating the solution to the
desired temperature, and then adding the pyridine ester derivative
I-1 all at once, intermittently, or continuously, either as such or
dissolved in a solvent, to bring about the reaction.
[0102] The resulting pyridine .beta.-ketoester derivative V can be
readily isolated by neutralizing the reaction solution with the
addition of an equivalent amount of acid relative to the base that
was used, by then extracting the product with methylene chloride,
toluene, xylene, benzene, chloroform, pentane, hexane, heptane or
the like, and by concentrating the extract. Examples of acids which
can be used for such purposes include carboxylic acids such as
acetic acid and formic acid, and inorganic acids such as
hydrochloric acid and sulfuric acid. The purity of the product can
be increased by recrystallization, if necessary.
[0103] Under these reaction conditions, depending on the
combination of the pyridine ester derivative I-1, the base, and the
ester compound IV, as well as the proportions in which they are
used, especially when using a metal alcoholate as the base or when
using an alcohol as the solvent, a transesterification reaction
sometimes progresses between the group represented by -X in the
pyridine ester derivative I-1, the group represented by --OR.sup.3
in the ester compound IV, the alcoholate moiety of the metal
alcoholate and the alcohol. In such cases, the product can become a
mixture of various types of moieties represented by --OR.sup.4 in
the pyridine .beta.-ketoester derivative V, but the purity of such
mixtures can be readily increased by common separation and
purification means such as distillation, column chromatography, and
recrystallization. These mixtures may also be used without any
problems in the next step (f) for obtaining the pyridine carbonyl
derivative II.
[0104] Step (f): Step for producing a pyridine carbonyl derivative
II by hydrolysis and decarboxylation of a pyridine .beta.-ketoester
derivative V.
[0105] The amount of water that is used for hydrolysis is not
particularly limited, although the use of at least one mole based
on one mole of the pyridine .beta.-ketoester derivative V is
preferred in view of obtaining the target pyridine carbonyl
derivative II with good yields, and no more than 100 mol water
based on one mole of the pyridine .beta.-ketoester derivative V is
usually preferred in view of the reaction rate, the extraction
efficiency following the reaction, the volume efficiency of the
equipment, and the like.
[0106] Any common acid or base used in the hydrolysis of esters can
be used in the hydrolysis reaction. Examples of acids include
inorganic acids such as hydrochloric acid and sulfuric acid, and
acidic gases such as hydrogen chloride gas can also be used.
Examples of bases include alkali metal hydroxides such as sodium
hydroxide and potassium hydroxide.
[0107] The intermediate product obtained by the hydrolysis of the
pyridine .beta.-ketoester derivative V is unstable under these
reaction conditions, and the pyridine carbonyl derivative II is
produced as a result of the rapid progress of the decarboxylation,
thus allowing the decarboxylation to be carried out, usually at the
same time as the hydrolysis, in the same reactor using the
unmodified acid or base used in the hydrolysis. More acid or base
can be added during the reaction to promote the hydrolysis and
decarboxylation. The type of acid or base that is added at such
times may be the same as, or different from, the acid or base
initially used in the hydrolysis and decarboxylation. The amount of
acid or base may be used within a range of preferably 0.001 to 100
mol, and more preferably 0.01 to 10 mol, based on one mole of the
pyridine .beta.-ketoester derivative V.
[0108] Methods for carrying out the reaction include methods in
which the hydrolysis and decarboxylation are first started under
basic conditions, and excess acid is added to the reaction system
midway during the reaction to bring about acidic conditions, and
methods in which the hydrolysis and decarboxylation are first
started under acidic conditions, and excess base is added to the
reaction system midway during the reaction to bring about basic
conditions.
[0109] To obtain the pyridine carbonyl derivative II, a reaction
mixture containing the pyridine .beta.-ketoester derivative V is
obtained by means of the reaction in step (e), and water and an
acid or base are then added to the reaction solution without
separating the pyridine .beta.-ketoester derivative V from the
reaction mixture to carry out the hydrolysis and decarboxylation in
step (f), allowing the pyridine carbonyl derivative II to be
obtained.
[0110] When the hydrolysis and decarboxylation in step (f) are then
carried out without isolating the pyridine .beta.-ketoester
derivative V from the reaction mixture obtained in the reaction in
step (e), the pyridine .beta.-ketoester derivative V contained in
the reaction mixture is quantified and analyzed, and the acid or
base is used in an amount within the range described above relative
to that amount. The amount of acid or base may be used within a
range of preferably 0.001 to 100 mol, and more preferably 0.01 to
10 mol, based on one mole of the pyridine ester derivative I-1 used
in step (e). The amount of water is used within a range of
preferably 1 to 100 mol based on the amount of the pyridine
.beta.-ketoester derivative V contained in the reaction mixture.
Water may also be used within a range of preferably 1 to 100 mol
based on one mole of the pyridine ester derivative I-1.
[0111] Because a base is already present in the reaction mixture
containing the pyridine .beta.-ketoester derivative V obtained in
step (e), the addition of water allows the existing base to act as
a promoter in the hydrolysis and decarboxylation. In this
embodiment, the neutralization in step (e) can be omitted.
[0112] The hydrolysis and decarboxylation may be carried out in the
presence of an organic solvent. The type of organic solvent is not
particularly limited, provided that the reaction is not adversely
affected, examples of which include aliphatic hydrocarbons such as
pentane, hexane, cyclohexane, octane and ligroin; aromatic
hydrocarbons such as benzene, toluene, xylene, cumene and
mesitylene; ethers such as diethyl ether, tetrahydrofuran and
dioxane; polyethers such as ethylene glycol dimethyl ether,
diethylene glycol dimethyl ether, triethylene glycol dimethyl
ether, tetraethylene glycol dimethyl ether, ethylene glycol diethyl
ether, diethylene glycol diethyl ether, triethylene glycol diethyl
ether and tetraethylene glycol diethyl ether; and alcohols such as
methanol, ethanol, propanol, isopropanol, butanol and t-butanol.
Among these, the use of aromatic hydrocarbons, ethers and
polyethers is preferred in view of the reaction rate, solubility of
the pyridine .beta.-ketoester derivative V, and the like. The
amount of solvent is not particularly limited, although it is
preferably used within a range of 0.5 to 100 weight parts based on
the pyridine .beta.-ketoester derivative V or the pyridine ester
derivative I-1.
[0113] When the hydrolysis and decarboxylation in step (f) are then
carried out without isolating the pyridine .beta.-ketoester
derivative V from the reaction mixture obtained in the reaction in
step (e), the solvent used in step (e) can be used as such in step
(f).
[0114] The reaction temperature is preferably within a range of 0
to 200.degree. C., and more preferably 10 to 150.degree. C.
[0115] The resulting pyridine carbonyl derivative II is isolated
and purified from the reaction mixture in the usual manner which
commonly used in the isolation and purification of organic
compounds. For example, after cooling the reaction mixture to room
temperature, it is extracted with an organic solvent such as
methylene chloride, toluene, xylene, benzene, chloroform, pentane,
hexane or heptane, the extract is washed with saline water, the
solvent is distilled off, and the residue is purified by
distillation, recrystallization, chromatography, or the like.
[0116] The pyridine carbonyl derivative II thus obtained can be
converted to the corresponding pyridine alcohol derivative III by
using the procedures in step (d).
[0117] Of the pyridine derivative represented by the General
Formula I-2 contained the pyridine derivative I, for example,
5-benzenesulfonylfuro[2- ,3-c]pyridine can be converted to the
intermediate noted in International Unexamined Patent Application
WO 96/35678 by the following method, and a compound having
antiviral activity can be derived by the method noted in the same
application.
[0118] That is, 5-benzenesulfonylfuro[2,3-c]pyridine is converted
to 5-cyanofuro[2,3-c]pyridine by reacting with an alkali metal
cyanide. The cyanation can be carried out with or without a
solvent. The solvent is not particularly limited, provided that the
reaction is not adversely affected, examples of which include polar
solvents such as dimethyl formamide, dimethyl sulfoxide,
1,3-dimethyl-2-imidazolidione. This reaction can also be carried
out as a two-phase reaction using an iphase-transfer catalyst. The
reaction is carried out by heating
5-benzenesulfonylfuro[2,3-c]pyridine and an excess amount of an
alkali metal cyanide at a temperature within a range of room
temperature to the reflux temperature. The resulting
5-cyanofuro[2,3-c]pyridine can be converted to
5-acetylfuro[2,3-c]pyridine by reacting with a methylating agent
such as methyllithium or methylmagnesium chloride. The amount of
the methylating agent is preferably within a range of 0.8 to 2 mol
based on the starting pyridine derivative.
[0119] 5-Acetylfuro[2,3-c]pyridine can be synthesized by reacting
an acetyl anion equivalent with
5-benzenesulfonylfuro[2,3-c]pyridine, and then subsequent
deprotection. Conventional acetyl anion equivalents can be used as
the acetyl anion equivalent, although preferred examples include
lactonitrile cyanhydrin ether, and acetyl anion equivalents
prepared from an acetaldehyde thioacetal, thioacetal monoxide or
the like and a strong base such as butyllithium, tert-butyllithium,
methyllithium, phenyllithium, lithium diisopropylamide, lithium
hexamethyldisilazide or sodium hexamethyldisilazide. The acetyl
anion equivalent is preferably used in an amount of 0.8 to 2 mol
based on one mole of the starting pyridine derivative.
[0120] The reaction may be carried out in a solvent that does not
adversely affect the reaction, examples of such solvents preferably
including ethers such as diethyl ether, tetrahydrofuran,
dimethoxyethane and dioxane. The reaction temperature is preferably
within the range of -40.degree. C. to 100.degree. C.
[0121] The resulting product is subsequently treated and
deprotected by a common method, and the resulting
5-acetylfuro[2,3-c]pyridine can be converted to the intermediate by
reduction with sodium borohydride, diisobutyl aluminum hydride,
lithium aluminum hydride or the like noted in International
Unexamined Patent Application WO 96/35678.
EXAMPLES
[0122] The present invention is described in further detail below
with reference to examples, but the present invention is not
limited in any way by these examples.
Example 1
[0123] 3-Methylfuran-2-carbaldehyde (14.8 g, 0.135 mol) was mixed
with hexane (50 mL), aniline (15.1 g, 0.162 mol) was added over 30
minutes at room temperature, and the mixture was heated to reflux
for 4 hours with stirrng. The mixture was allowed to cool to room
temperature, and the solvent was then distilled off to give 28.1 g
of the crude product of
3-methylfuran-2-carbaldehyde-N-phenylimine.
[0124] Benzenesulfonyl cyanide (90.2 g, 0.540 mol) and ethyl
chloroformate (29.3 g, 0.270 mol) were mixed at room temperature in
xylene (125 mL) and were stirred to reflux at a temperature of 120
to 140.degree. C. A xylene (75 mL) solution of the crude
3-methylfuran-2-carbaldehyde-N-phenylimine (28.1 g) obtained above
was added dropwise over 2 hours to the mixture. After all the
solution had been added, the reaction mixture was heated to reflux
for 3 hours, it was then cooled to room temperature, and the
solvent was distilled off to give 81.3 g of crude product. This
product was purified by column chromatography on silica gel, giving
17.2 g of 5-benzenesulfonylfuro[2,3-c]pyridine.
[0125] .sup.1H-NMR spectra (270 MHz, CDCl.sub.3, TMS, ppm) .delta.:
6.99 (1H, dd, J=2.16 Hz, 0.81 Hz), 7.49 to 7.62 (3H, m), 7.91 (1H,
d, J=2.16 Hz), 8.07 to 8.11 (2H, m), 8.56 (1H, d, J=0.81 Hz), 8.90
(1H, s).
[0126] As is apparent from Example 1, the present invention can
provide a method by which pyridine derivatives that are useful as
intermediates for antiviral agents and the like can be produced
with good yields in an industrially useful manner under moderate
conditions.
Example 2
[0127] Ethyl cyanoformate (21.4 g, 0.216 mol) and
3-methylfuran-2-carbalde- hyde-N-phenylimine(10.0 g, 54.1 mmol)
were mixed at room temperature in xylene (50 mL) then heated to
reflux at 120 to 140.degree. C. with stirring. A xylene (30 mL)
solution of 11.7 g (0.108 mol) of ethyl chloroformate was added
dropwise for an hour to the resulting mixture. After all the
solution had been added, the reaction mixture was heated to reflux
for 2 hours, it was allowed to cool to room temperature, and the
solvent was distilled off to give 14.0 g of crude product. This
product was purified by column chromatography on silica gel, giving
5.40 g (52.3% yield) of 5-ethoxycarbonylfuro[2,3-c]pyridine.
[0128] .sup.1H-NMR spectra (270 MHz, CDCl.sub.3, TMS, ppm) .delta.:
1.47 (3H, t, J=7.16 Hz), 4.51 (2H, q, J=7.16 Hz), 6.94 (1H, dd,
J=2.70 Hz, 1.08 Hz), 7.85 (1H, d, J=2.70 Hz), 8.50 (1H, d, J=1.08
Hz), 8.99 (1H, s).
Example 3
[0129] n-Butyl cyanoformate(13.7 g, 0.108 mol) and
3-methylfuran-2-carbald- ehyde-N-phenylimine (5.0 g, 27.0 mmol)
were mixed at room temperature in xylene (25 mL) then heated to
reflux at 120 to 140.degree. C. with stirring. A xylene (15 mL)
solution of 7.40 g (54.2 mol) of n-butyl chloroformate was added
dropwise for an hour to the resulting mixture. After all the
solution had been added, the reaction mixture was heated to reflux
for 2 hours, it was allowed to cool to room temperature, and the
solvent was distilled off to give 7.10 g of crude product. This
product was purified by column chromatography on silica gel, giving
2.71 g (45.8% yield) of 5-n-butoxycarbonylfuro[2,3-c]pyridine.
[0130] .sup.1H-NMR spectra (270 MHz, CDCl.sub.3, TMS, ppm) .delta.:
0.99 (3H, t, J=7.43 Hz), 1.49 (2H, tq, J=7.43 Hz), 1.84 (2H, tt,
J=7.43 Hz), 4.45 (2H, t, J=7.43 Hz), 6.94 (1H, dd, J=2.43 Hz,
J=0.81 Hz), 7.85 (1H, d, J=2.43 Hz), 8.48 (1H, d, J=0.81 Hz), 8.99
(1H, s).
Example 4
[0131] 5-Ethoxycarbonylfuro[2,3-c]pyridine obtained in Example
2(3.82 g, 20.0 mmol) was dissolved in tetrahydrofuran (50 mL) and
cooled to -30.degree. C. To the cooled solution, 22.0 mL (22.0 mol)
of 1.0 M solution of methyllithium/diethyl ether was added, and the
solution was stirred for 2 hours at the same temperature, the
reaction mixture was then poured into 100 mL of 5% ammonium
chloride aqueous solution which had been cooled on ice, and the
product was extracted twice with 100 mL of ethyl acetate. After
washing with 100 mL of saturated sodium bicarbonate aqueous
solution and 100 mL of saturated saline water, the extract was
concentrated to give 3.12 g of crude product. This product was
purified by column chromatography on silica gel, giving 2.48 g
(77.0% yield) of 5-acetylfuro[2,3-c]pyridine.
[0132] .sup.1H-NMR spectra (270 MHz, CDCl.sub.3, TMS, ppm) .delta.:
2.79 (3H, s), 6.94 (1H, dd, J=2.16 Hz, J=1.08 Hz), 7.83 (1H, d,
J=2.16 Hz), 8.39 (1H, d, J=1.08 Hz), 8.91 (1H, s).
Example 5
[0133] 5-Acetylfuro[2,3-c]pyridine obtained in Example 4 (2.42 g,
15.0 mmol) was dissolved in toluene (30 mL), and the solution was
cooled to 0.degree. C. To the cooled solution, 16.0 mL (16.0 mmol)
of 1.0 M solution of diisobutyl aluminum hydride in toluene
solution was added, and the solution was stirred for 2 hours at the
same temperature, the reaction mixture was then poured into 100 mL
of a 5% ammonium chloride aqueous solution which had been cooled on
ice, and it was extracted twice with 100 mL of ethyl acetate. After
washing with 100 mL of saturated sodium bicarbonate aqueous
solution and 100 mL of saturated saline water, the extract was
concentrated to give 2.36 g of crude product. This product was
purified by column chromatography on silica gel, giving 2.25 g
(92.0% yield) of 5-(1-hydroxyethyl)furo[2,3-c]pyridine.
[0134] As is apparent from Examples 2 to 5, the present invention
can provide a method by which pyridine alcohol derivatives that are
useful as intermediates for antiviral agents and the like can be
produced with good yields in an industrially useful manner under
moderate conditions. It also provides synthetic intermediates and a
method of producing them giving such the method.
Example 6
[0135] 5-Ethoxycarbonylfuro[2,3-c]pyridine obtained in Example 2
(956 mg, 5.0 mmol) was dissolved in 10 mL of toluene, 2.55 g (7.5
mmol) of a 20% ethanol solution of sodium ethoxide was added
dropwise at room temperature to the solution, and 661 mg (7.5 mmol)
of ethyl acetate was then added dropwise at room temperature with
stirring. After all the ethyl acetate had been added, the reaction
mixture was heated to 80.degree. C., and a reaction was carried out
for 8 hours. The reaction solution was then cooled to 5.degree. C.
and was neutralized with 450 mg (7.5 mmol) of acetic acid as the
temperature was held 5-10.degree. C., the solution was stirred for
30 minutes as the temperature was maintained, 1 mL of water was
added, and the solution was returned to room temperature. The
organic layer was separated, the aqueous layer was extracted twice
with 5 mL of methylene chloride, and the combined organic layer was
dried with anhydrous magnesium sulfate and then concentrated in a
rotary evaporator to give 851 mg of solids. This solids were
recrystallized from a mixed solvent of toluene-hexane, giving 769
mg (66% yield) of ethyl .beta.-oxo-5-furo[2,3-c]pyridinepropionate
in a purity of 99% by HPLC.
[0136] .sup.1H-NMR spectra (270 MHz, CDCl.sub.3, TMS, ppm) .delta.:
1.25 (3H, t, J=7.17 Hz), 4.21 (2H, q, J=7.17 Hz), 4.25 (2H, s),
6.95 (1H, d, J=2.46 Hz), 7.85 (1H, d, J=1.97 Hz), 8.42 (1H, s),
8.88 (1H, s).
Example 7
[0137] 5-Ethoxycarbonylfuro[2,3-c]pyridine (956 mg, 5.0 mmol) was
dissolved in 10 mL of toluene, 510 mg (7.5 mmol) of sodium ethoxide
was added at room temperature to the solution, and 661 mg (7.5
mmol) of ethyl acetate was then added dropwise at room temperature
with stirring. After all the ethyl acetate had been added, the
reaction mixture was heated to 80.degree. C., and a reaction was
carried out for 4 hours. The reaction solution was then cooled to
5.degree. C. and was neutralized with 450 mg (7.5 mmol) of acetic
acid as the temperature was held 5-10.degree. C., the solution was
stirred for 30 minutes as the temperature was maintained, 1 mL
water was then added, and the solution was returned to room
temperature. The organic layer was separated, the aqueous layer was
extracted twice with 5 mL of methylene 5 chloride, and the combined
organic layer was dried with anhydrous magnesium sulfate and then
concentrated in a rotary evaporator, and the resulting solids were
recrystallized from a mixed solvent of toluene-hexane, giving 840
mg (72% yield) of ethyl .beta.-oxo-5-furo[2,3-c]pyridinepropionate
in a purity of 99% by HPLC.
Example 8
[0138] As 510 mg (7.5 mmol) of sodium ethoxide was stirred in 5 mL
toluene, 1.16 g (10.0 mmol) of t-butyl acetate was added dropwise
at room temperature to the solution. Then, 956 mg (5.0 mmol) of
5-ethoxycarbonylfuro[2,3-c]pyridine dissolved in 5 mL of toluene
was added dropwise at room temperature to the above solution. After
all the solution had been added, the reaction mixture was heated to
60.degree. C., and a reaction was carried out for 3 hours. The
reaction solution was then cooled to 5.degree. C. and was
neutralized with 450 mg (7.5 mmol) of acetic acid as the
temperature was held 5-10.degree. C., the solution was stirred for
30 minutes as the temperature was maintained, 1 mL water was then
added, and the solution was returned to room temperature. The
organic layer was separated, the aqueous layer was extracted twice
with 5 mL of methylene chloride, and the combined organic layer was
dried with anhydrous magnesium sulfate and then concentrated in a
rotary evaporator. The resulting solids were recrystallized from a
mixed solvent of toluene-hexane mixture, giving 933 mg (80% yield)
of ethyl .beta.-oxo-5-furo[2,3-c]pyridinepropionate in a purity of
99% by HPLC.
Example 9
[0139] As 405 mg (7.5 mmol) of sodium methoxide was stirred in 5 mL
toluene, 1.16 g (10.0 mmol) of t-butyl acetate was added dropwise
at room temperature to the solution. Then, 956 mg (5.0 mmol) of
5-ethoxycarbonylfuro[2,3-c]pyridine was dissolved in 5 mL of
toluene was added dropwise at room temperature to the above
solution. After all the solution had been added, the reaction
mixture was heated to 60.degree. C., and a reaction was carried out
for 3 hours. The reaction solution was then cooled to 5.degree. C.
and was neutralized with 450 mg (7.5 mmol) of acetic acid as the
temperature was held 5-10.degree. C., the solution was stirred for
30 minutes as the temperature was maintained, 1 mL water was then
added, and the solution was returned to room temperature. The
organic layer was separated, the aqueous layer was extracted twice
with 5 mL of methylene chloride, and the combined organic layer was
dried with anhydrous magnesium sulfate and then concentrated in a
rotary evaporator to give 971 mg solids. NMR analysis revealed
those to be a mixture of methyl
.beta.-oxo-5-furo[2,3-c]pyridinepropionate, ethyl
.beta.-oxo-5-furo[2,3-c]pyridinepropionate, and tert-butyl
.beta.-oxo-5-furo[2,3-c]pyridinepropionate (molar ratio of
55:44:1). The NMR spectra for the aforementioned ethyl
.beta.-oxo-5-furo[2,3-c]pyridine- propionate were consistent with
those of the ethyl .beta.-oxo-5-furo[2,3-c- ]pyridinepropionate
obtained in Example 6.
[0140] Methyl .beta.-oxo-5-furo[2,3-c]pyridinepropionate
[0141] .sup.1H-NMR spectra (270 MHz, CDCl.sub.3, TMS, ppm) .delta.:
3.75 (3H, s), 4.29 (2H, s), 6.95 (1H, d, J=1.97 Hz), 7.85 (1H, d,
J=1.98 Hz), 8.39 (1H, s), 8.88 (1H, s).
[0142] tert-Butyl .beta.-oxo-5-furo[2,3-c]pyridinepropionate
[0143] .sup.1H-NMR spectra (270 MHz, CDCl.sub.3, TMS, ppm) .delta.:
1.42 (9H, s), 4.13 (2H, s), 6.94 (1H, d, J=1.98 Hz), 7.83 (1H, d,
J=1.98 Hz), 8.40 (1H, s), 8.88 (1H, s).
Example 10
[0144] The 971 mg of the mixture of methyl
.beta.-oxo-5-furo[2,3-c]pyridin- epropionate, ethyl
.beta.-oxo-5-furo[2,3-c]pyridinepropionate, and tert-butyl
.beta.-oxo-5-furo[2,3-c]pyridinepropionate (molar ratio of 55:44:1)
obtained in Example 9 was dissolved in 20 mL of toluene, and 1.04 g
of 35% hydrochloric acid was added at room temperature with
stirring. After addition, the reaction mixture was heated to
60.degree. C., and a reaction was carried out for 3 hours with
stirring. The reaction solution was then cooled to room temperature
and was neutralized with 8.40 g of 5% sodium hydroxide aqueous
solution. The organic layer was separated, the aqueous layer was
extracted twice with 5 mL of methylene chloride, and the combined
organic layer was dried with anhydrous magnesium sulfate and then
concentrated in a rotary evaporator. The resulting solids were
recrystallized from a mixed solvent of toluene-hexane, giving 629
mg of 5-acetylfuro[2,3-c]pyridine in a purity of 99% by HPLC (78%
yield from 5-ethoxycarbonylfuro[2,3-c]pyridine).
Example 11
[0145] Ethyl .beta.-oxo-5-furo[2,3-c]pyridinepropionate (1.17 g,
5.0 mmol) was dissolved in 20 mL of toluene, and 1.5 mL (7.5 mmol)
of 10 N sulfuric acid was added at room temperature with stirring.
After addition, the reaction mixture was heated to 80.degree. C.,
and a reaction was carried out for 6 hours with stirring. The
solution was then cooled to room temperature and neutralized with
12 mL of 5% sodium hydroxide aqueous solution. The organic layer
was separated, the aqueous layer was extracted twice with 5 mL of
methylene chloride, and the combined organic layer was dried with
anhydrous magnesium sulfate and then concentrated in a rotary
evaporator. The resulting solids were recrystallized from a mixed
solvent of toluene-hexane, giving 580 mg of
5-acetylfuro[2,3-c]pyri- dine in a purity of 99% by HPLC (72%
yield).
Example 12
[0146] Ethyl .beta.-oxo-5-furo[2,3-c]pyridinepropionate (583 mg,
2.5 mmol) obtained in Example 7 was dissolved in 10 mL of toluene,
and 3 g of 10% sodium hydroxide aqueous solution was added with
stirring. After addition, the reaction mixture was heated to
60.degree. C., and a reaction was carried out for 8 hours with
stirring. It was then cooled to room temperature, the organic layer
was separated, the aqueous layer was extracted twice with 5 mL of
methylene chloride, -.and the combined organic layer was dried with
anhydrous magnesium sulfate and then concentrated in a rotary
evaporator. The resulting solids were recrystallized from a mixed
solvent of toluene-hexane, giving 205 mg (51% yield) of
5-acetylfuro[2,3-c]pyridine in a purity of 99% by HPLC.
Example 13
[0147] As 405 mg (7.5 mmol) of sodium methoxide was stirred in 5 mL
of toluene, 1.16 g (10.0 mmol) of tert-butyl acetate was added
dropewise at room temperature to the solution. Then, 956 mg (5.0
mmol) of 5-ethoxycarbonylfuro[2,3-c]pyridine dissolved in 5 mL of
toluene was added dropwise at room temperature to the above
solution. After all the solution had been added, the reaction
mixture was heated to 60.degree. C., a reaction was carried out for
3 hours. The resulting reaction mixture was then neutralized with
450 mg (7.5 mmol) of acetic acid, the solution was stirred for 30
minutes, 1.5 mL (7.5 mmol) of 5 N hydrochloric acid was then added,
and the solution was stirred for 5 hours at 60.degree. C. to carry
out a reaction. The solution was then returned to room temperature,
the organic layer was separated, the aqueous layer was extracted
twice with 5 mL of methylene chloride, and the combined organic
layer was dried with anhydrous magnesium sulfate and then
concentrated in a rotary evaporator. The resulting solids were
recrystallized from a mixed solvent of toluene-hexane, giving 580
mg (72% yield) of 5-acetylfuro[2,3-c]pyridine in a purity of 99% by
HPLC.
Example 14
[0148] 5-Acetylfuro[2,3-c]pyridine (2.42 g, 15.0 mmol) obtained by
the method in Example 13 was dissolved in toluene (30 mL), and the
solution was cooled to 0.degree. C. To the cooled solution, 16.0 mL
(16.0 mmol) of 1.0 M solution of diisobutyl aluminum hydride in
toluene was added, and the solution was stirred for 2 hours at this
temperature, the reaction mixture was then poured into 100 mL of a
5% ammonium chloride aqueous solution which had been cooled on ice,
and it was extracted twice with 100 mL of ethyl acetate. The
extract was washed with 100 mL of saturated sodium bicarbonate
aqueous solution and 100 mL of saturated saline water, and the
solvent was concentrated to give 2.36 g of crude product. This
product was purified by column chromatography on silica gel, giving
2.25 g (92.0% yield) of 5-(1-hydroxyethyl)furo[2,3-c]pyridine.
[0149] .sup.1H-NMR spectra (270 MHz, CDCl.sub.3, TMS, ppm) .delta.:
1.55 (3H, s), 4.03 (1H, s), 4.99 (1H, q, J=5.93 Hz), 6.80 (1H, d,
J=1.98 Hz), 7.53 (1H, s), 7.77 (1H, d, J=2.47 Hz), 8.80 (1H,
s).
[0150] As is apparent from Examples 6 to 14, the present invention
can provide methods by which pyridine derivatives that are useful
as intermediates for antiviral agents and the like can be produced
with good yields in an industrially useful manner under moderate
conditions. It also provides synthetic intermediates and methods of
producing them giving such the methods.
[0151] The entire disclosure of the specifications, claims and
summaries of Japanese Patent Applications No. 9-291075 filed on
Oct. 23, 1997, No. 10-64862 filed on Mar. 16, 1998 and No.
10-219943 filed Aug. 4, 1988 is herein incorporated by
reference.
* * * * *