U.S. patent application number 16/639899 was filed with the patent office on 2020-11-19 for method for producing isocyanates.
The applicant listed for this patent is Covestro Deutschland AG. Invention is credited to Franz Beggel, Daniela Cozzula, Andreas Ernst, Christoph Guertler, Gernot Jaeger, Jens Langanke, Walter Leitner, Matthias Leven, Thomas Ernst Mueller, Stefan Wershofen.
Application Number | 20200361856 16/639899 |
Document ID | / |
Family ID | 1000005037475 |
Filed Date | 2020-11-19 |
United States Patent
Application |
20200361856 |
Kind Code |
A1 |
Cozzula; Daniela ; et
al. |
November 19, 2020 |
METHOD FOR PRODUCING ISOCYANATES
Abstract
The invention relates to a method for producing an isocyanate,
wherein a carbamate or thiolcarbomate is converted, in the presence
of a catalyst, with separation of an alcohol or thioalcohol, at a
temperature of at least 150.degree. C., to the corresponding
isocyanate, wherein a compound of the general formula (X)(Y)(Z--H)
is used as a catalyst, in particular characterized in that the
compound has both a proton donor function and a proton acceptor
function. In the catalysts according to the invention, a separable
proton is bound to a heteroatom, which is more electronegative than
carbon. Said heteroatom is either identical to Z or a component
thereof. In the catalysts according to the invention, there is
additionally a proton acceptor function which is either identical
to X or a component thereof. According to the invention, the proton
donator and proton acceptor function are connected to each other by
the bridge Y.
Inventors: |
Cozzula; Daniela; (Sankt
Katharinen, DE) ; Ernst; Andreas; (Aachen, DE)
; Leven; Matthias; (Koln, DE) ; Leitner;
Walter; (Aachen, DE) ; Mueller; Thomas Ernst;
(Aachen, DE) ; Guertler; Christoph; (Koln, DE)
; Wershofen; Stefan; (Monchengladbach, DE) ;
Jaeger; Gernot; (Koln, DE) ; Beggel; Franz;
(Koln, DE) ; Langanke; Jens; (Mechernich,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Covestro Deutschland AG |
Leverkusen |
|
DE |
|
|
Family ID: |
1000005037475 |
Appl. No.: |
16/639899 |
Filed: |
August 31, 2018 |
PCT Filed: |
August 31, 2018 |
PCT NO: |
PCT/EP2018/073512 |
371 Date: |
February 18, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01J 31/0208 20130101;
C07C 263/04 20130101; B01J 31/0238 20130101; B01J 31/0225 20130101;
B01J 27/055 20130101; B01J 2231/64 20130101; B01J 2531/002
20130101 |
International
Class: |
C07C 263/04 20060101
C07C263/04; B01J 31/02 20060101 B01J031/02; B01J 27/055 20060101
B01J027/055 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 4, 2017 |
EP |
17189248.2 |
Claims
1. A process for producing an isocyanate in which a carbamate or
thiolcarbamate is converted into the corresponding isocyanate in
the presence of a catalyst with elimination of an alcohol or
thioalcohol at a temperature of at least 150.degree. C., wherein
the catalyst used comprises a compound of the general formula
(X)(Y)(Z--H), where: (A) X is N(R.sup.1), Y is C(R.sup.2) or is a
bridge formed of 2 carbon atoms which are part of a ring system
comprising 5 or 7 carbon atoms with alternating double and single
bonds, or is a bridge formed of 3, 5 or 7 carbon atoms with
alternating single and double bonds, and Z is O, S, N(R.sup.6) or
N.sup.(+)(R.sup.7)(R.sup.8), and wherein the catalyst has a
pK.sub.B at 25.degree. C. of .gtoreq.3.00; or (B) X is O, --Y is
C(R.sup.2) or is a bridge formed of 2 carbon atoms which are part
of a ring system comprising 5 or 7 carbon atoms with alternating
double and single bonds, or is a bridge formed of 3, 5 or 7 carbon
atoms with alternating single and double bonds, and Z is O; or (C)
X is O, --Y is S(O)(R.sup.3) or P(OR.sup.4)(OR.sup.5), and Z is O;
where: R.sup.1 is: an optionally substituted aromatic or
araliphatic radical having 6 to 10 carbon atoms, or an optionally
substituted aliphatic radical having 1 to 6 carbon atoms, or joined
to R.sup.2 or R.sup.8 to form a ring consisting of a total of 5 to
8 atoms, wherein the ring can optionally comprise heteroatoms,
especially nitrogen and/or sulfur; R.sup.2 is: hydrogen, or an
optionally substituted, aromatic or araliphatic radical having 6 to
10 carbon atoms, or an optionally substituted, aliphatic radical
having 1 to 6 carbon atoms and optionally comprising ether units,
or joined to R.sup.1 or R.sup.6 or R.sup.7 to form a ring
consisting of a total of 5 to 8 atoms, wherein the ring can
optionally comprise one or more heteroatoms; R.sup.3 is an aromatic
or araliphatic radical having 6 to 10 carbon atoms which is
substituted by a sulfonic acid group or sulfonate group, or an
aliphatic radical having 1 to 6 carbon atoms which is substituted
by an amine group, sulfonic acid group or sulfonate group, or
O.sup.(-)M.sup.(+), where M.sup.(+) is an alkali metal cation,
imidazolium cation, pyridinium cation, pyrrolidinium cation,
phosphonium cation, sulfonium cation or NH.sub.4.sup.+, or is a
mono-, di-, tri- or tetrasubstituted organic ammonium cation the
organic substituents of which independently of one another are
selected from the group consisting of methyl, ethyl, propyl, butyl,
pentyl, hexyl, phenyl and cyclohexyl; R.sup.4 and R.sup.5
independently of one another are: optionally substituted aromatic
or araliphatic radicals each having 6 to 10 carbon atoms, where
R.sup.4 and R.sup.5 may be joined to form a ring consisting of 5 to
8 atoms, or optionally substituted aliphatic radicals each having 1
to 6 carbon atoms, where R.sup.4 and R.sup.5 may be joined to form
a ring consisting of 5 to 8 atoms; R.sup.6 is: an optionally
substituted aromatic or araliphatic radical having 6 to 10 carbon
atoms or an optionally substituted aliphatic radical having 1 to 6
carbon atoms or joined to R.sup.2 to form a ring consisting of a
total of 5 to 8 atoms, wherein the ring can optionally comprise one
or more heteroatoms; R.sup.7 is: an optionally substituted aromatic
or araliphatic radical having 6 to 10 carbon atoms, or an
optionally substituted aliphatic radical having 1 to 6 carbon
atoms, or joined to R.sup.2 to form a ring consisting of a total of
5 to 8 atoms, wherein the ring can optionally comprise one or more
heteroatoms; R.sup.8 is: an optionally substituted aromatic or
araliphatic radical having 6 to 10 carbon atoms, or an optionally
substituted aliphatic radical having 1 to 6 carbon atoms, or joined
to R.sup.1 to form a ring consisting of a total of 5 to 8
atoms.
2. The process as claimed in claim 1, in which the conversion of
the starting carbamate or starting thiolcarbamate is conducted in
solution in the presence of an organic solvent selected from
aprotic polar solvents without isocyanate-reactive groups.
3. The process as claimed in claim 2, in which a concentration of
the starting carbamate or starting thiolcarbamate in the solution
is 5% by mass to 95% by mass, based on the total mass of the
solution.
4. The process as claimed in claim 1, in which a molar ratio of
starting carbamate or starting thiolcarbamate to catalyst of 1000:1
to 1:1 is used.
5. The process as claimed in claim 1, in which the conversion is
conducted at a temperature in the range from 150.degree. C. to
280.degree. C. and at a pressure in the range from 0.001
bar.sub.(abs.) to 2.00 bar.sub.(abs.).
6. The process as claimed in claim 1, in which the isocyanate
formed and/or the alcohol or thioalcohol formed is/are removed from
the reaction mixture continuously or at intervals.
7. The process as claimed in claim 6, wherein the removal of the
alcohol or thioalcohol is effected by passing through a stripping
gas and/or by distillation, optionally assisted by application of a
pressure which is reduced compared to ambient pressure.
8. The process as claimed in claim 6, wherein either (i) both the
isocyanate formed and the alcohol or thioalcohol formed are removed
together, followed by a separation of a gaseous mixture obtained
containing the isocyanate and the alcohol or thioalcohol by means
of fractional condensation, or (ii) first the alcohol or
thioalcohol and then the isocyanate is removed.
9. The process as claimed in claim 8, in which, for the removal of
the alcohol or thioalcohol and of the isocyanate, the reaction
mixture is distilled continuously in two series-connected
distillation columns.
10. The process as claimed in claim 1, in which: the isocyanate to
be produced is butylene 1,4-diisocyanate, pentane 1,5-diisocyanate,
hexamethylene 1,6-diisocyanate or the dimers, trimers, pentamers,
heptamers or nonamers thereof or mixtures of same, isophorone
diisocyanate, 2,2,4- and/or 2,4,4-trimethylhexamethylene
diisocyanate, the isomeric bis(4,4'-isocyanatocyclohexyl)methanes
or mixtures thereof in any desired proportions, cyclohexylene
1,4-diisocyanate, phenyl isocyanate, phenylene 1,4-diisocyanate,
tolylene 2,4- and/or 2,6-diisocyanate, naphthylene
1,5-diisocyanate, diphenylmethane 2,2'- and/or 2,4'- and/or
4,4'-diisocyanate and/or the higher homologs thereof, 1,3- and/or
1,4-bis(2-isocyanatoprop-2-yl)benzene,
1,3-bis(isocyanatomethyl)benzene, or an alkyl
2,6-diisocyanatohexanoate (lysine diisocyanate) having alkyl groups
of 1 carbon atom to 6 carbon atoms, and the carbamate or
thiolcarbamate used is the methyl, ethyl, n-propyl, isopropyl,
n-butyl, isobutyl, tert-butyl, cyclohexyl or phenyl carbamate or
thiolcarbamate or substituted methyl, ethyl, n-propyl, isopropyl,
n-butyl, isobutyl, tert-butyl, cyclohexyl or phenyl carbamate or
thiolcarbamate which corresponds to the isocyanate to be
produced.
11. The process as claimed in claim 1, in which no further catalyst
is used besides the catalyst (X)(Y)(Z)H.
12. The process as claimed in claim 1, in which the catalyst
(X)(Y)(Z--H) is selected from the group consisting of
2-hydroxy-2,4,6-cycloheptatrien-1-one (tropolone);
2-acetyl-1-tetralone; N,N'-diphenylformamidine;
N-(2,6-dimethylphenyl)-5,6-dihydro-4H-1,3-thiazin-2-amine
(xylazine); 2,3-dihydro-7-azaindole; protonated
N-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene; protonated
1,8-diazabicyclo[5.4.0]undec-7-ene;
O-methyl-N,N'-diisopropylisourea; 2-mercaptopyridine;
1,3,4-thiadiazole-2,5-dithiol; mercaptobenzimidazole (k); the
constitutional isomers of the benzenedisulfonic acid monoanion; the
constitutional isomers of benzenedisulfonic acid;
(R)-(-)-1,1'-binaphthyl-2,2'-hydrogenphosphate; dibenzyl
hydrogenphosphate; naphthalene-2,6-disulfonic acid monoanion;
alkali metal hydrogensulfate, 2-aminoethane-1-sulfonic acid
(taurine) and mixtures thereof.
13. The process as claimed in claim 1, in which a catalyst of type
(A) is used.
14. The process as claimed in claim 1, in which a catalyst of type
(B) is used.
15. The process as claimed in claim 1, in which a catalyst of type
(C) is used.
Description
[0001] The invention relates to a process for producing an
isocyanate in which a carbamate or thiolcarbamate is converted into
the corresponding isocyanate in the presence of a catalyst with
elimination of an alcohol or thioalcohol at a temperature of at
least 150.degree. C., wherein the catalyst used is a compound of
general formula (X)(Y)(Z--H) which is especially characterized in
that it has both a proton donor function and a proton acceptor
function. In the catalysts according to the invention, an
abstractable proton is bonded to a heteroatom that is more
electronegative than carbon. This heteroatom is either identical to
Z or is a constituent thereof. A proton acceptor function which is
either identical to X or is a constituent thereof is further
present in the catalysts according to the invention. The proton
donor function and proton acceptor function are joined to one
another via the bridge Y.
[0002] Isocyanates are produced in large volumes and serve mainly
as starting materials for the production of polyurethanes. They are
usually produced by reacting the corresponding amines with
phosgene. The reaction of the amines with the phosgene can be
effected either in the gas phase or in the liquid phase, wherein
the reaction may be conducted discontinuously or continuously.
There is global use both of aromatic isocyanates, for example
methylene diphenyl diisocyanate (MMDI--"monomeric MDI"),
polymethylene polyphenylene polyisocyanate (a mixture of MMDI and
higher homologs, PMDI, "polymeric MDI") or tolylene diisocyanate
(TDI), and of aliphatic isocyanates, for example pentane
diisocyanate (PDI), hexamethylene diisocyanate (HDI) or isophorone
diisocyanate (IPDI).
[0003] One alternative to the reaction of primary amines with
phosgene is carbamate cleavage:
R--NH--(C.dbd.O)--O--R'.fwdarw.R--N.dbd.C.dbd.O+H--O--R'
[0004] R and R' denote organic radicals. It is also possible to
convert thio/carbamates R--NH--(C.dbd.O)--S--R' into isocyanates
with elimination of a thioalcohol H--S--R'.
[0005] The carbamate cleavage can be effected thermally or be
mediated by catalysts or stoichiometrically employed auxiliary
reagents. The thermal cleavage generally takes place above a
temperature of approx. 180.degree. C. As catalysts or auxiliary
reagents for the catalytic carbamate cleavage, a very wide variety
of classes of compounds have been described. Some examples are
mentioned below:
[0006] A publication in Tetrahedron Letters (43), 2002, 1673-1676
(P. Uriz et al.) is concerned with the use of the phyllosilicate
montmorillonite K10 as a catalyst for the carbamate cleavage. It is
hypothesized here that the carbamates are protonated via the
Bronsted acid centers present and are cleaved by subsequent
transprotonation to give the isocyanate and alcohol.
[0007] CN 000101337189 also describes the use of solid acids of the
type SO42-/TiO.sub.2--ZnO--ZrO.sub.2-Al.sub.2O.sub.3 prepared from
titanates (8 to 45 mol %), water-soluble zinc salts (30 to 60 mol
%), water-soluble aluminum salts (3 to 10 mol %), water-soluble
zirconium salts (8 to 20 mol %) and also sulfuric acid (6 to 18 mol
%).
[0008] A publication in J. Org. Chem. (63), 2000, 3239-3240 (S.
Gastaldi et al.) describes the use of diisopropylethylamine
("Hunig's base") and SiI.sub.2H.sub.2 in the carbamate cleavage.
Both are used stoichiometrically in this case.
[0009] Patent application EP 0 672 653 A1 describes the production
of isocyanates by carbamate cleavage at 150.degree. C. to
350.degree. C. in the presence of organic sulfonic acids of the
type R.sup.1SO.sub.3H or salts thereof. R' here is an organic
radical which may be substituted by groups that do not react with
isocyanates, for example halogen, alkoxy or nitro groups. Specific
examples mentioned are a number of aromatic (e.g.
naphthalene-.beta.-sulfonic acid) and aliphatic (e.g.
methanesulfonic acid) sulfonic acids and also alkali metal salts of
aromatic (sodium meta-xylene-4-sulfonate) and aliphatic (potassium
methanesulfonate) sulfonic acids. Catalysts having a proton donor
function and proton acceptor function within the meaning of the
present invention are not disclosed. In particular, this
application does not disclose using aromatic or araliphatic
disulfonic acids or the monoanions of such disulfonic acids as
catalysts.
[0010] The Japanese patent application JP 2011/162442 also deals
with carbamate cleavage. Catalysts disclosed are the metal salts of
non-coordinating anions. Non-coordinating anions disclosed are
perfluoroalkylsulfonate, arylsulfonate, hexafluorophosphate,
tetrafluoroborate, tetrakis(pentafluorophenyl)borate and also
tetrakis[3,5-bis(trifluoromethyl)phenyl]borate. Preference is given
to arylsulfonic acid anions, especially
CH.sub.3C.sub.6H.sub.4SO.sub.3.sup.(-) (toluenesulfonate).
Catalysts having an additional proton donor function are not
disclosed. In particular, no disclosure of monoanions of aromatic
or araliphatic disulfonic acids as suitable catalysts is
provided.
[0011] The Korean application with the number 19930018854 (also
published as KR970004412) describes the production of isocyanates
R'--NCO from thionecarbamates and (stoichiometrically employed)
halopyridinium salts in the presence of tertiary amines such as
triethylamine, pyridine, quinoline, quinoxaline,
hexamethylenetetramine, 1,4-diazabicyclo[2.2.2]octane,
1,5-diazabicyclo[4.3.0]non-5-ene and
1,8-diazabicylco[5.4.0]undec-7-ene according to the equation:
##STR00001##
(X=F, Cl, I; R=alkyl radical; R'=aliphatic or aromatic radical)
[0012] The subject matter of the present invention, the formation
of isocyanates by cleavage of carbamates or thiolcarbamates (which
both have an --NH--(C.dbd.O) structural unit) with liberation of
alcohols or thioalcohols, relates to a completely different
chemical reaction. It is therefore not surprising that none of the
tertiary amine catalysts disclosed in this document satisfies the
conditions of a catalyst (X)(Y)(Z--H) of the present invention.
[0013] U.S. Pat. No. 4,081,472 describes conducting carbamate
cleavages in the presence of metal ions of groups I-B, II-B, III-A,
IV-A, IV-B, V--B and VIII, especially copper, zinc, aluminum, tin,
titanium, vanadium, iron, cobalt and nickel ions. Said metal ions
are used inter alia in the form of salts of carboxylic acids, in
the form of alkoxides or thioalkoxides, in the form of phenoxides,
salts of organic sulfonic acids, in the form of chelating complexes
(by way of example of acetylacetonate) and in the form of salts of
amino acids. Metal-free catalysts or catalysts containing metals at
most as a catalytically inactive counterion are not disclosed in
this document.
[0014] US 2016/0145201 A1 describes a multistage process for
producing meta-xylidene diisocyanate in which inorganic acids such
as sulfuric or phosphoric acid are used. The use of salts or
organic esters of such acids as catalysts for the cleavage of
carbamates is not disclosed in this document.
[0015] Despite advances in the field of phosgene-free isocyanate
production in general and carbamate cleavage in particular, there
is a continuing need for improvement in these phosgene-free
synthesis routes. Although the carbamate cleavage can proceed
uncatalyzed, suitable catalysts are still being sought which
greatly accelerate the desired reaction without undesired side
reactions and/or further reactions proceeding to a significant
extent, that is to say which have a high selectivity for isocyanate
formation.
[0016] Taking this need into account, the present invention
provides a process for producing an isocyanate in which a carbamate
or thiolcarbamate is converted into the corresponding isocyanate at
a temperature of at least 150.degree. C. in the presence of a
catalyst with elimination of an alcohol or thioalcohol, wherein the
catalyst used is a compound of the general formula
(X)(Y)(Z--H)
where: [0017] (A) [0018] X is N(R.sup.1), [0019] Y is C(R.sup.2), a
bridge formed of 2 carbon atoms which are part of a ring system
composed of 5 or 7 carbon atoms with alternating double and single
bonds, or is a bridge formed of 3, 5 or 7 carbon atoms with
alternating single and double bonds, and [0020] Z is O, S,
N(R.sup.6) or N.sup.(+)(R.sup.7)(R.sup.8), [0021] wherein the
catalysts of type (A) have a pK.sub.B at 25.degree. C. of
.gtoreq.3.00; [0022] or (B) [0023] X is O, [0024] --Y is
C(R.sup.2), a bridge formed of 2 carbon atoms which are part of a
ring system composed of 5 or 7 carbon atoms with alternating double
and single bonds, or is a bridge formed of 3, 5 or 7 carbon atoms
with alternating single and double bonds, and [0025] Z is O; [0026]
or (C) [0027] X is O, [0028] Y is S(O)(R.sup.3) or
P(OR.sup.4)(OR.sup.5), and [0029] Z is O; [0030] where: [0031]
R.sup.1 is [0032] an optionally substituted aromatic or araliphatic
radical having 6 to 10 carbon atoms or [0033] an optionally
substituted aliphatic radical having 1 to 6 carbon atoms or [0034]
joined to R.sup.2 or R.sup.8 to form a ring consisting of a total
of 5 to 8 atoms, wherein the ring can optionally comprise
heteroatoms, especially nitrogen and/or sulfur; [0035] R.sup.2 is
[0036] hydrogen or [0037] an, optionally substituted, aromatic or
araliphatic radical having 6 to 10 carbon atoms or [0038] an,
optionally substituted, aliphatic radical having 1 to 6 carbon
atoms and optionally comprising ether units or [0039] joined to
R.sup.1 or R.sup.6 or R.sup.7 to form a ring consisting of a total
of 5 to 8 atoms, wherein the ring can optionally comprise
heteroatoms, especially nitrogen and/or sulfur; [0040] R.sup.3 is
[0041] an aromatic or araliphatic radical having 6 to 10 carbon
atoms which is substituted by a sulfonic acid group or sulfonate
group or [0042] an aliphatic radical having 1 to 6 carbon atoms
which is substituted by an amine group, sulfonic acid group or
sulfonate group or [0043] OHM.sup.(+), where M.sup.(+) is an alkali
metal cation, imidazolium cation, pyridinium cation, pyrrolidinium
cation, phosphonium cation, sulfonium cation, NH.sub.4.sup.+, or is
a mono-, di-, tri- or tetrasubstituted organic ammonium cation the
organic substituents of which independently of one another are
selected from the group consisting of methyl, ethyl, propyl, butyl,
pentyl, hexyl, phenyl and cyclohexyl, where M.sup.(+) particularly
preferably is an alkali metal cation or NH.sub.4.sup.+, very
particularly preferably is an alkali metal cation selected from
Li.sup.+, Na.sup.+ or K.sup.+; [0044] R.sup.4 and R.sup.5
independently of one another are [0045] optionally substituted
aromatic or araliphatic radicals each having 6 to 10 carbon atoms,
where R.sup.4 and R.sup.5 may be joined to form a ring consisting
of 5 to 8 atoms; [0046] optionally substituted aliphatic radicals
each having 1 to 6 carbon atoms, where R.sup.4 and R.sup.5 may be
joined to form a ring consisting of 5 to 8 atoms; [0047] R.sup.6 is
[0048] an optionally substituted aromatic or araliphatic radical
having 6 to 10 carbon atoms or [0049] an optionally substituted
aliphatic radical having 1 to 6 carbon atoms or [0050] joined to
R.sup.2 to form a ring consisting of a total of 5 to 8 atoms,
wherein the ring can optionally comprise heteroatoms, especially
nitrogen and/or sulfur; [0051] R.sup.7 is [0052] an optionally
substituted aromatic or araliphatic radical having 6 to 10 carbon
atoms or [0053] an optionally substituted aliphatic radical having
1 to 6 carbon atoms or [0054] joined to R.sup.2 to form a ring
consisting of a total of 5 to 8 atoms, wherein the ring can
optionally comprise heteroatoms, especially nitrogen and/or sulfur;
[0055] R.sup.8 is [0056] an optionally substituted aromatic or
araliphatic radical having 6 to 10 carbon atoms or [0057] an
optionally substituted aliphatic radical having 1 to 6 carbon atoms
or joined to R.sup.1 to form a ring consisting of a total of 5 to 8
atoms.
[0058] Carbamates which can be used according to the invention have
the general formula R--NH--(C.dbd.O)--O--R', in which R and R.sup.1
denote organic radicals (particularly preferred radicals R and R'
are listed further below). According to the invention,
thiolcarbamates (also referred to as thiolurethanes) are understood
to be compounds of the type R--NH--(C.dbd.O)--S--R', in which an
S-organyl group (S--R') is bonded to the carbon atom of the
carbonyl group. (A distinction should be made between these and
thionecarbamates (thioneurethanes) R--NH--(C.dbd.S)--O--R', in
which in comparison to carbamates the oxygen atom of the carbonyl
group has been replaced by sulfur. The label thiocarbamates
(thiourethanes) is frequently used as a generic term for both
substance classes.) In this respect, see also scheme 1 below.
##STR00002##
[0059] In the terminology of this invention, the terms carbamate
and thiolcarbamate of course also encompass compounds having more
than one, especially having two or more, carbamate or
thiolcarbamate groups. Such further carbamate or thiolcarbamate
groups are then part of the radical R of the structural formulae
from scheme 1.
[0060] The catalysts mentioned feature both a proton donor function
and a proton acceptor function. In the catalysts according to the
invention, an abstractable proton (H.sup.+) is bonded to a
heteroatom which is more electronegative than carbon. This
heteroatom is either identical to Z (Z.dbd.O:Z--H.dbd..O--H) or is
a constituent thereof (e.g. the nitrogen atom when
Z.dbd.N(R.sup.6):Z--H.dbd.C.sub.6H.sub.5(N.)H). A proton acceptor
function which is either identical to X (X.dbd.O) or is a
constituent thereof (e.g. the nitrogen atom when
X.dbd.N(R'):X.dbd.C.sub.6H.sub.5--N:) is further present in the
catalysts according to the invention. According to the invention,
(X) and "Z" in (Z--H) are covalently connected to one another via
(Y). This connection can be realized by a bridge formed of 2 carbon
atoms or by a bridge formed of 3, 5 or 7 carbon atoms with
alternating single and double bonds. The connection can also be
realized by a single carbon atom ((Y).dbd.C(R.sup.2)).
[0061] An example of a catalyst of type (A) is
##STR00003##
having a pK.sub.B of 3.25, in which: Z.dbd.N(R.sup.6),
Y.dbd.C(R.sup.2) and X.dbd.N(R.sup.1), where firstly R.sup.1 and
R.sup.2 are joined to form a ring of 6 atoms which contains the
heteroatom N (namely the "pyridine" nitrogen), and secondly R.sup.6
and R.sup.2 are joined to form a ring of 5 atoms which contains the
heteroatom N (namely the nitrogen bearing the proton). In this
example, the five- and the six-membered ring share two carbon
atoms; this is expressly encompassed by the invention (but of
course is not mandatory). Further, in this example the carbon atom
in C(R.sup.2) is part both of the ring that is formed by the
joining of R.sup.1 and R.sup.2 and of the ring that is formed by
the joining of R.sup.6 and R.sup.2; this too is expressly
encompassed by the invention. Within the context of this invention,
the pK.sub.B values calculated according to Advanced Chemistry
Development (ACD/Labs) Software V11.02 for 25.degree. C. are
considered to be definitive. These have been tabulated for numerous
organic compounds and are accessible via the substance search of
the Chemical Abstracts Service SCIFINDER.RTM. database under
Substance Detail, Predicted Properties, Chemical. In the case of
compounds of type (A) having a plurality of basic groups, the
inventive requirement of a minimum pK.sub.B of 3.00 has to be
satisfied by the most strongly basic group.
[0062] A further example of a catalyst of type (A) is
##STR00004##
in which Z.dbd.S, Y.dbd.C(R.sup.2), X.dbd.N(R), with R.sup.1 being
joined to R.sup.2 to form a ring consisting of 5 atoms (the
imidazole ring). In this example, the imidazole ring resulting from
the joining of R.sup.1 and R.sup.2 is fused with a benzene ring;
this is expressly encompassed by the invention.
[0063] An example of a catalyst of type (B) is
##STR00005##
in which: Z.dbd.O, Y=bridge formed of 2 carbon atoms which are part
of a ring system of 7 carbon atoms with alternating single and
double bonds, and X.dbd.O.
[0064] An example of a catalyst of type (C) is
##STR00006##
in which: Z.dbd.O, Y.dbd.P(OR.sup.4)(OR.sup.5) and X.dbd.O, where
in addition R.sup.4 and R.sup.5 are araliphatic radicals each
having 7 carbon atoms.
[0065] Without wishing to be bound to a theory, it is assumed that
the presence of proton donor function and proton acceptor function
in the same molecule permits a proton shift which is essential for
the carbamate or thiolcarbamate cleavage. This is also supported by
the fact that the catalysts mentioned can be formally represented
in structural formulae in which the proton donor function and
proton acceptor function are linked by alternating atom-atom single
bonds and atom-atom double bonds.
[0066] There firstly follows a brief summary of various possible
embodiments of the invention:
[0067] In a first embodiment of the invention, which can be
combined with all other embodiments, the conversion of the starting
carbamate or starting thiolcarbamate is conducted in solution in
the presence of an organic solvent selected from aprotic polar
solvents without isocyanate-reactive groups.
[0068] In a second embodiment of the invention, which is a
particular configuration of the first embodiment, the organic
solvent is selected from diphenyl ether, sulfolane, cyclic
propylene carbonate or an ionic liquid (especially
1-butyl-3-methylimidazolium hydrogensulfate,
1-butyl-3-methylimidazolium methanesulfonate and/or
trihexyltetradecylphosphonium
bis(2,4,4-trimethylpentyl)phosphinate).
[0069] In a third embodiment of the invention, which is a
particular configuration of the first and second embodiments, a
concentration of the starting carbamate or starting thiolcarbamate
in the solution is set in the range from 5% by mass to 95% by mass,
preferably in the range from 10% by mass to 20% by mass, based on
the total mass of the solution.
[0070] In a fourth embodiment of the invention, which can be
combined with all other embodiments, a molar ratio of starting
carbamate or starting thiolcarbamate to catalyst of 1000:1 to 1:1,
preferably of 100:1 to 10:1, is used.
[0071] In a fifth embodiment of the invention, which can be
combined with all other embodiments, the conversion is conducted at
a temperature in the range from 150.degree. C. to 280.degree. C.
and at a pressure in the range from 0.001 bar.sub.(abs.) to 2.00
bar.sub.(abs.), particularly preferably at a temperature in the
range from 160.degree. C. to 260.degree. C. and at a pressure in
the range from 0.001 bar.sub.(abs.) to 1.00 bar.sub.(abs.), very
particularly preferably at a temperature in the range from
180.degree. C. to 240.degree. C. and at a pressure in the range
from 0.001 bar.sub.(abs.) to 1.00 bar.sub.(abs.).
[0072] In a sixth embodiment of the invention, which can be
combined with all other embodiments, the conversion is conducted
continuously or discontinuously in a reactor selected from the
group consisting of stirred tanks, stirred tank cascades,
distillation columns and tubular reactors.
[0073] In a seventh embodiment of the invention, which is a
particular configuration of the sixth embodiment, a residence time
of the reaction mixture in the reactor is set in the range from 0.5
h to 10 h, preferably in the range from 1.0 h to 8.0 h,
particularly preferably in the range from 1.5 h to 6.0 h.
[0074] In an eighth embodiment of the invention, which can be
combined with all other embodiments, the isocyanate formed and/or
the alcohol or thioalcohol formed is removed from the reaction
mixture continuously or at intervals.
[0075] In a ninth embodiment of the invention, which is a
particular configuration of the eighth embodiment, the alcohol or
thioalcohol formed is removed from the reaction mixture
continuously or at intervals, wherein the removal of the alcohol or
thioalcohol is effected by passing through a stripping gas
(preferably nitrogen or a noble gas such as in particular helium or
argon) and/or by distillation, optionally assisted by application
of a pressure which is reduced compared to ambient pressure.
[0076] In a tenth embodiment of the invention, which is a further
particular configuration of the eighth embodiment, the isocyanate
formed and the alcohol or thioalcohol formed are removed from the
reaction mixture continuously or at intervals, wherein either (i)
both are removed together, followed by a separation of the gaseous
mixture obtained containing the isocyanate and the alcohol or
thioalcohol by means of fractional condensation, or (ii) first the
alcohol or thioalcohol and then the isocyanate is removed from the
reaction mixture. The removal of the isocyanate formed is
advantageously effected by distillation; in the case of variant (i)
the isocyanate formed and the alcohol or thioalcohol formed are in
this case distilled off from the reaction mixture together, wherein
the distillation may be assisted by passing through a stripping gas
(preferably nitrogen or a noble gas such as in particular helium or
argon). In the case of variant (ii) the removal of the alcohol or
thioalcohol can be effected by passing through a stripping gas
(preferably nitrogen or a noble gas such as in particular helium or
argon) and/or by distillation; the removal of the isocyanate is
preferably effected by distillation, with the passing through of a
stripping gas (preferably nitrogen or a noble gas such as in
particular helium or argon) being able to be used to assist,
however.
[0077] In an eleventh embodiment of the invention, which is a
particular configuration of the tenth embodiment, the reaction
mixture is distilled continuously in two series-connected
distillation columns in order to remove the alcohol or thioalcohol
and the isocyanate.
[0078] In a twelfth embodiment of the invention, which can be
combined with all other embodiments, the isocyanate to be produced
is [0079] butylene 1,4-diisocyanate, pentane 1,5-diisocyanate,
hexamethylene 1,6-diisocyanate or the dimers, trimers, pentamers,
heptamers or nonamers thereof or mixtures of same, isophorone
diisocyanate, 2,2,4- and/or 2,4,4-trimethylhexamethylene
diisocyanate, the isomeric bis(4,4'-isocyanatocyclohexyl)methanes
or mixtures thereof in any desired proportions, cyclohexylene
1,4-diisocyanate, phenyl isocyanate, phenylene 1,4-diisocyanate,
tolylene 2,4- and/or 2,6-diisocyanate, naphthylene
1,5-diisocyanate, diphenylmethane 2,2'- and/or 2,4'- and/or
4,4'-diisocyanate and/or the higher homologs thereof, 1,3- and/or
1,4-bis(2-isocyanatoprop-2-yl)benzene,
1,3-bis(isocyanatomethyl)benzene, or an alkyl
2,6-diisocyanatohexanoate (lysine diisocyanate) having alkyl groups
of 1 carbon atom to 6 carbon atoms, and the carbamate or
thiolcarbamate used is the [0080] methyl, ethyl, n-propyl,
isopropyl, n-butyl, isobutyl, tert-butyl, cyclohexyl or phenyl
carbamate or thiolcarbamate [0081] or [0082] substituted methyl,
ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl,
cyclohexyl or phenyl carbamate or thiolcarbamate which corresponds
to the isocyanate to be produced.
[0083] In a thirteenth embodiment of the invention, which can be
combined with all other embodiments, no further catalyst is used
besides the catalyst (X)(Y)(Z)H.
[0084] In a fourteenth embodiment of the invention, which can be
combined with all other embodiments, the catalyst (X)(Y)(Z--H) is
selected from the group consisting of [0085]
2-hydroxy-2,4,6-cycloheptatrien-1-one (tropolone) (a);
2-acetyl-1-tetralone (b); N,N'-diphenylformamidine (c);
N-(2,6-dimethylphenyl)-5,6-dihydro-4H-1,3-thiazin-2-amine
(xylazine) (d); 2,3-dihydro-7-azaindole (e); protonated
N-methyl-1,5,7-tri azabicyclo[4.4.0]dec-5-ene (f); protonated
1,8-diazabicyclo[5.4.0]undec-7-ene (g);
O-methyl-N,N'-diisopropylisourea (h); 2-mercaptopyridine (i);
1,3,4-thiadiazole-2,5-dithiol (j); mercaptobenzimidazole (k); the
constitutional isomers of the benzenedisulfonic acid monoanion (l);
the constitutional isomers of benzenedisulfonic acid (m);
(R)-(-)-1,1'-binaphthyl-2,2'-hydrogenphosphate (n); dibenzyl
hydrogenphosphate (o); naphthalene-2,6-disulfonic acid monoanion
(p); alkali metal hydrogensulfate (q), 2-aminoethane-1-sulfonic
acid (taurine) (r) and mixtures (s) of the compounds mentioned.
[0086] In a fifteenth embodiment of the invention, which can be
combined in particular (but not only) with the fourteenth
embodiment, the catalysts used are those of type (A), preferably
exclusively those of type (A).
[0087] In a seventeenth embodiment of the invention, which can be
combined in particular (but not only) with the fourteenth
embodiment, the catalysts used are those of type (B), preferably
exclusively those of type (B).
[0088] In an eighteenth embodiment of the invention, which can be
combined in particular (but not only) with the fourteenth
embodiment, the catalysts used are those of type (C), preferably
exclusively those of type (C).
[0089] The embodiments briefly outlined above and further possible
configurations of the invention are elucidated in more detail
hereinafter. Various embodiments are combinable with one another as
desired unless the opposite is clearly apparent to those skilled in
the art from the context.
[0090] Starting carbamates usable according to the invention can be
obtained via various routes known per se. Examples include the
transesterification of N-arylurea derivatives with alcohols
(described for example in J. Wang et al., Applied Catalysis A:
General, 2004, 261, 191-197), the reductive carbonylation of
nitroaromatics with carbon monoxide and alcohols (described for
example in M. vGasperini et al., Adv. Syn. Cat., 2005, 347,
105-120), the oxidative carbonylation of amines with carbon
monoxide and oxygen (described for example in S. Fukuoka, M. Chono,
M. Kohno, J. Chem. Soc., Chem. Commun., 1984, 399) and the reaction
of primary amines with organic carbonates (described for example in
U.S. Pat. No. 8,871,965 B2).
[0091] According to the invention, preference is given to the
reaction of primary amines with organic carbonates, which proceeds
according to
R--NH.sub.2+R'.sub.2CO.sub.3.fwdarw.R--NH--(C.dbd.O)--O--R'+R'--OH
[0092] Preference is given to using processes such as are described
for example in WO 2014/187756 A1 and the literature references
cited therein. These reactions are catalyzed for example by zinc
clusters, zinc salts or Lewis acids.
[0093] Starting thiolcarbamates usable according to the invention
can be obtained via various routes known per se. Examples from the
specialist literature have been disclosed for example in
Tetrahedron 50 (1994) 5669-5680, Tetrahedron 59 (2003) 1327-1331,
Tetrahedron 60 (2004) 2869-2873, Tetrahedron 61 (2005) 7153-7175,
J. Org. Chem. 68 (2003) 3733-3735, J. Org. Chem. 70 (2005)
2551-2554 and U.S. Pat. No. 4,486,449. Starting thiolcarbamates
usable according to the invention are particularly preferably
obtained by the carbonylation of amines with carbon monoxide,
sulfur and alkyl halides.
[0094] The conversion of the starting carbamate or starting
thiolcarbamate is preferably conducted in solution. Suitable
solvents are especially aprotic polar solvents without
isocyanate-reactive groups. Preference is given to diphenyl ether,
sulfolane, cyclic propylene carbonate or ionic liquids (especially
1-butyl-3-methylimidazolium hydrogensulfate,
1-butyl-3-methylimidazolium methanesulfonate and/or
trihexyltetradecylphosphonium
bis(2,4,4-trimethylpentyl)phosphinate). The concentration of the
starting carbamate or starting thiolcarbamate in the solution is
preferably in the range from 5% by mass to 95% by mass,
particularly preferably in the range from 10% by mass to 20% by
mass, based on the total mass of the solution. Preference is given
to using a molar ratio of starting carbamate or starting
thiolcarbamate to catalyst of 1000:1 to 1:1, preferably of 100:1 to
10:1. However, a solvent-free synthesis is also possible.
[0095] The process according to the invention is preferably
performed at a temperature in the range from 150.degree. C. to
280.degree. C. and at a pressure in the range from 0.001
bar.sub.(abs.) to 2.00 bar.sub.(abs.), particularly preferably at a
temperature in the range from 160.degree. C. to 260.degree. C. and
at a pressure in the range from 0.001 bar.sub.(abs.) to 1.00
bar.sub.(abs.), very particularly preferably at a temperature in
the range from 180.degree. C. to 240.degree. C. and at a pressure
in the range from 0.001 bar.sub.(abs.) to 1.00 bar.sub.(abs.). The
process according to the invention can be carried out either
continuously or discontinuously ("batchwise"). Suitable reactors
for performing the process are especially stirred tanks or stirred
tank cascades, distillation columns (reactive distillation) or
tubular reactors. The residence time of the reaction mixture in the
reactor used is in this case preferably from 0.5 h to 10 h,
particularly preferably from 1.0 h to 8.0 h, very particularly
preferably from 1.5 h to 6.0 h.
[0096] It is particularly preferable to remove the isocyanate
formed and/or the alcohol or thioalcohol formed from the reaction
mixture continuously or at intervals. This can be effected by
passing through a stripping gas (preferably nitrogen or a noble gas
such as in particular helium or argon) and/or by distillation,
optionally assisted by application of a pressure which is reduced
compared to ambient pressure. In particular in the case of
distillation, the conditions can be selected here such that both
are distilled off together. In this case it is preferable to
separate the mixture distilled off, obtained in gaseous form and
containing the isocyanate to be produced and the alcohol or
thioalcohol (and also any low-boiling secondary components) in two
or more steps by fractional condensation, and in this way to obtain
the isocyanate and the alcohol or thioalcohol.
[0097] It is also conceivable to remove only the lower-boiling
component (generally the alcohol or thioalcohol) from the reaction
mixture (less preferred), or to first remove the lower-boiling and
then the higher-boiling (more preferred). In a continuous mode of
operation, the last-mentioned variant can be realized in the
simplest case by connecting two distillation columns in series. In
the case of polycarbamates or polythiolcarbamates, it should be
ensured that the corresponding polyisocyanate (usually a
diisocyanate) is only distilled off once all carbamate or
thiolcarbamate groups of the starting compound have been converted
into isocyanate groups (unless the target product were a mixed
(thiolo)carbamate isocyanate, which generally however will not be
the case).
[0098] Suitable carbamates are in particular those carbamates that
can be traced back retrosynthetically to the reaction of [0099] (1)
primary, secondary or tertiary (optionally substituted) aliphatic
monoalcohols R--OH' such as [0100] methanol, ethanol, n-propanol,
isopropanol, n-butanol, isobutanol, tert-butanol, the higher
homologs thereof, cyclohexanol, with the primary monoalcohols being
preferred, [0101] or (optionally substituted) phenol [0102] with
[0103] (2) isocyanates R--NCO such as [0104] butylene
1,4-diisocyanate, pentane 1,5-diisocyanate (PDI), hexamethylene
1,6-diisocyanate (HDI) or the dimers, trimers, pentamers, heptamers
or nonamers thereof or mixtures of same, isophorone diisocyanate
(IPDI), 2,2,4- and/or 2,4,4-trimethylhexamethylene diisocyanate,
the isomeric bis(4,4'-isocyanatocyclohexyl)methanes or mixtures
thereof in any desired proportions, cyclohexylene 1,4-diisocyanate,
phenyl isocyanate, phenylene 1,4-diisocyanate, tolylene 2,4- and/or
2,6-diisocyanate (TDI), naphthylene 1,5-diisocyanate,
diphenylmethane 2,2'- and/or 2,4'- and/or 4,4'-diisocyanate (MDI)
and/or higher homologs (polymeric MDI), 1,3- and/or
1,4-bis(2-isocyanatoprop-2-yl)benzene (TMXDI),
1,3-bis(isocyanatomethyl)benzene (XDI), and also alkyl
2,6-diisocyanatohexanoates (lysine diisocyanates) having alkyl
groups of 1 carbon atom to 6 carbon atoms.
[0105] Suitable thiolcarbamates are in particular compounds that
can be traced back retrosynthetically to the reaction of the
monothioalcohols R'--SH (1'-replacement of O by S) corresponding to
the previously mentioned monoalcohols (1) with the mentioned
isocyanates (2). Particular preference is given here to
thiomethanol, thioethanol, thioisopropanol and (optionally
substituted) thiophenol.
[0106] In the formulae R--NH--(C.dbd.O)--O--R' and
R--NH--(C.dbd.O)--S--R', R therefore corresponds to the radical of
the isocyanate (that is to say e.g. C.sub.6H.sub.5 in the case of
phenyl isocyanate; in the case of isocyanates having more than one
isocyanate group the corresponding carbamate also has the
appropriate number of carbamate functions R'--O--(CO)--NH--) and
R.sup.1 corresponds to the radical of the monoalcohol (e.g.
CH.sub.3 in the case of methanol).
[0107] In the case of substituted alkyl carbamates or alkyl
thiolcarbamates (R--NH--(CO)--O--R'), the aliphatic radical R.sup.1
bears substituents which independently of one another are selected
from the group consisting of CN, NO.sub.2, F, Cl, Br, I, OR'',
where R'' is an alkyl group, especially is CH.sub.3,
C.sub.2H.sub.6, n-C.sub.3H.sub.7, n-C.sub.4H.sub.9,
i-C.sub.4H.sub.9, t-C.sub.4H.sub.9, n-C.sub.5H.sub.11; or
n-C.sub.6H.sub.13, and R has the same meaning as above. Here, at
least one hydrogen atom of the aliphatic radical R.sup.1 has been
replaced by one of the mentioned substituents.
[0108] In the case of substituted phenyl carbamates
(R--NH--(CO)--O--C.sub.6H.sub.m-5A.sub.m) or phenyl thiolcarbamates
(R--NH)--(CO)--S--C.sub.6H.sub.m-5A.sub.m), the aromatic
six-membered ring bears up to m substituents A which independently
of one another are selected from the group consisting of CN,
NO.sub.2, F, Cl, Br, I, OH, COOH, COCl, COOR'', OR'', CH.sub.3,
C.sub.2H.sub.6, n-C.sub.3H.sub.7, iso-C.sub.3H.sub.7, where m is a
natural number in the range from 0 to 5, preferably from 0 to 4,
particularly preferably from 0 to 1, and R'' is an alkyl group,
especially is CH.sub.3, C.sub.2H.sub.6, n-C.sub.3H.sub.7,
iso-C.sub.3H.sub.7, n-C.sub.4H.sub.9, iso-C.sub.4H.sub.9,
tert-C.sub.4H.sub.9, n-O.sub.5H.sub.11 or n-C.sub.6H.sub.13, and R
has the same meaning as above.
[0109] In all embodiments of the invention, it is preferable not to
use any other catalysts besides the catalyst (X)(Y)(Z)H. The
process according to the invention thus makes it possible--apart
from a possibly used metallic cation in the case of salt-type
catalysts--to completely dispense with metal-containing catalysts,
which has the advantage that the process as a whole becomes more
environmentally friendly and requires a less complicated workup of
the crude product. This means both that a less intense purification
of the product is necessary since catalyst residues are less toxic
and thus can remain in the product and also that resulting waste
can be disposed of more simply. In addition, the use of metals,
especially in the region of the nobler metals, that is customary in
the prior art is often associated with high costs.
[0110] In addition to the catalyst structures (X)(Y)(Z)H
themselves, the conversion products thereof formed under reaction
conditions may also be catalytically active.
[0111] The catalyst (X)(Y)(Z)H is preferably selected from the
group consisting of (see also scheme 2 below)
2-hydroxy-2,4,6-cycloheptatrien-1-one (tropolone) (a);
2-acetyl-1-tetralone (b); shown below in the "enol form";
N,N'-diphenylformamidine (c; pKB=6.30);
N-(2,6-dimethylphenyl)-5,6-dihydro-4H-1,3-thiazin-2-amine
(xylazine) (d; pKB=6.33); 2,3-dihydro-7-azaindole (e; pKB=3.25);
protonated N-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (f);
protonated 1,8-diazabicyclo[5.4.0]undec-7-ene (g);
O-methyl-N,N'-diisopropylisourea (h; pK.sub.B=4.15);
2-mercaptopyridine (i; pKB=4.24); 1,3,4-thiadiazole-2,5-dithiol (j;
pKB=8.34); mercaptobenzimidazole (k); the constitutional isomers of
the benzenedisulfonic acid monoanion (=sulfobenzenesulfonate) (l);
the constitutional isomers of benzenedisulfonic acid (m);
(R)-(-)-1,1'-binaphthyl-2,2'-hydrogenphosphate (n); dibenzyl
hydrogenphosphate (o); naphthalene-2,6-disulfonic acid monoanion
(p); alkali metal hydrogensulfate (q), 2-aminoethane-1-sulfonic
acid (taurine) (r) and mixtures (s) of the compounds mentioned. For
the protonated compounds (salts) (f) and (g), no pK.sub.B values
are documented in the literature as of the current state of
knowledge; however it will be apparent to those skilled in the art
that these compounds satisfy the inventive criterion
(pK.sub.B.gtoreq.3.00), since both are already protonated and thus
have an extremely low tendency to accept a further proton (and
therefore the pK.sub.B is higher compared to the unprotonated
species).
##STR00007## ##STR00008## ##STR00009##
[0112] In one embodiment of the invention, catalysts of type (A)
are used, in particular exclusively those of type (A). Particular
preference is given here to the catalysts of type (A) mentioned in
scheme 2.
[0113] In another embodiment of the invention, catalysts of type
(B) are used, in particular exclusively those of type (B).
Particular preference is given here to the catalysts of type (B)
mentioned in scheme 2.
[0114] In one embodiment of the invention, catalysts of type (C)
are used, in particular exclusively those of type (C). Particular
preference is given here to the catalysts of type (C) mentioned in
scheme 2.
[0115] Of the catalysts mentioned in scheme 2, very particular
preference is given to alkali metal hydrogensulfate (especially
sodium hydrogensulfate) (q)), and benzene-1,3-disulfonic acid
monoanion (3-sulfobenzenesulfonate) (1) (both of type (C)).
[0116] Catalysts usable according to the invention are commercially
available or at least obtainable by known methods. For instance,
catalysts in protonated form ((f) and (g)) are obtainable for
example by reacting the neutral form with the acid A-H, by way of
example trifluoromethanesulfonic acid. The compounds (1) and (p)
can for example be obtained by reacting the corresponding dianions,
for example the disodium salts, with an acid such as in particular
sulfuric acid or trifluoromethanesulfonic acid.
[0117] The invention will be elucidated in yet more detail below on
the basis of examples.
EXAMPLES
[0118] The experiments were performed in standard laboratory
apparatuses. The reaction vessels were inertized with argon.
Phenanthrene was used as an internal standard for quantitative HPLC
analysis.
Example 1: Conversion of Methyl N-Phenylcarbamate into Phenyl
Isocyanate by Thermal Cleavage at 200.degree. C. in Diphenyl Ether
(Comparative Example without Catalyst)
[0119] In an inertized multi-neck flask, 0.61 g (3.42 mmol) of
phenanthrene were dissolved in 29.34 g (172.38 mmol) of diphenyl
ether. The reaction mixture was heated to 215.degree. C. In an
inertized Schlenk tube, 4.97 g (32.88 mmol) of methyl
N-phenylcarbamate were heated to 150.degree. C. Completely
transferring the methyl N-phenylcarbamate into the reaction mixture
resulted in a mixture having a temperature of 200.degree. C. This
temperature was held constant for 120 minutes. The gaseous reaction
products formed were driven out at an argon inert gas flow of 10
l/h and collected in a cold trap. The progress of the reaction was
monitored by means of continuous sampling from the reaction vessel
and subsequent analysis by means of .sup.1H NMR spectroscopy.
[0120] The yield of phenyl isocyanate was 20% with a selectivity of
91%.
Example 2: Conversion of Methyl N-Phenylcarbamate into Phenyl
Isocyanate by Thermal Cleavage at 200.degree. C. in Sulfolane
(Comparative Example without Catalyst)
[0121] In an inertized multi-neck flask, 0.75 g (4.21 mmol) of
phenanthrene were dissolved in 25.14 g (209.20 mmol) of sulfolane.
The reaction mixture was heated to 217.degree. C. In an inertized
Schlenk tube, 6.35 g (42.01 mmol) of methyl N-phenylcarbamate were
heated to 150.degree. C. Completely transferring the methyl
N-phenylcarbamate into the reaction mixture resulted in a mixture
having a temperature of 200.degree. C. This temperature was held
constant for 120 minutes. The gaseous reaction products formed were
driven out at an argon inert gas flow of 10 l/h and collected in a
cold trap. The progress of the reaction was monitored by means of
continuous sampling from the reaction vessel and subsequent
analysis by means of .sup.1H NMR spectroscopy.
[0122] The yield of phenyl isocyanate was 17% with a selectivity of
87%.
Example 3: Conversion of Methyl N-Phenylcarbamate into Phenyl
Isocyanate by Cleavage at 60.degree. C. in the Presence of Sodium
3-Sulfobenzenesulfonate at a Molar Ratio of Carbamate to Catalyst
of 19.5:1 (Comparative Example at Excessively Low Temperature for
the Catalyst Concentration Chosen)
[0123] In an inertized multi-neck flask, 0.59 g (3.31 mmol) of
phenanthrene and also 0.65 g (1.71 mmol) of sodium
3-sulfobenzenesulfonate were suspended in 30.01 g (176.31 mmol) of
diphenyl ether. 5.03 g (33.27 mmol) of methyl N-phenylcarbamate
were added to this reaction mixture and heated to 60.degree. C.
This temperature was held constant for 120 minutes. The gaseous
reaction products formed were driven out at an argon inert gas flow
of 10 l/h and collected in a cold trap. The progress of the
reaction was monitored by means of continuous sampling from the
reaction vessel and subsequent analysis by means of NMR
spectroscopy.
[0124] No isocyanate formation could be observed.
Example 4: Conversion of Methyl N-Phenylcarbamate into Phenyl
Isocyanate by Cleavage at 200.degree. C. in the Presence of Sodium
3-Sulfobenzenesulfonate (Catalyst of Type (C)) at a Molar Ratio of
Carbamate to Catalyst of 21.3:1
[0125] In an inertized multi-neck flask, 0.60 g (3.37 mmol) of
phenanthrene and also 0.59 g (1.55 mmol) of sodium
3-sulfobenzenesulfonate were suspended in 30.01 g (176.31 mmol) of
diphenyl ether. The reaction mixture was heated to 215.degree. C.
In an inertized Schlenk tube, 4.99 g (33.01 mmol) of methyl
N-phenylcarbamate were heated to 150.degree. C. Completely
transferring the methyl N-phenylcarbamate into the reaction mixture
resulted in a mixture having a temperature of 200.degree. C. This
temperature was held constant for 120 minutes. The gaseous reaction
products formed were driven out at an argon inert gas flow of 10
l/h and collected in a cold trap. The progress of the reaction was
monitored by means of continuous sampling from the reaction vessel
and subsequent analysis by means of NMR spectroscopy.
[0126] The yield of phenyl isocyanate was 32% with a selectivity of
74%.
Example 5: Conversion of Methyl N-Phenylcarbamate into Phenyl
Isocyanate by Cleavage at 240.degree. C. in the Presence of Sodium
3-Sulfobenzenesulfonate (Catalyst of Type (C)) at a Molar Ratio of
Carbamate to Catalyst of 19.5:1
[0127] In an inertized multi-neck flask, 0.60 g (3.37 mmol) of
phenanthrene and also 0.66 g (1.74 mmol) of sodium
3-sulfobenzenesulfonate were suspended in 30.11 g (176.90 mmol) of
diphenyl ether. The reaction mixture was heated to 261.degree. C.
In an inertized Schlenk tube, 5.13 g (33.94 mmol) of methyl
N-phenylcarbamate were heated to 178.degree. C. Completely
transferring the methyl N-phenylcarbamate into the reaction mixture
resulted in a mixture having a temperature of 240.degree. C. This
temperature was held constant for 120 minutes. The gaseous reaction
products formed were driven out at an argon inert gas flow of 10
l/h and collected in a cold trap. The progress of the reaction was
monitored by means of continuous sampling from the reaction vessel
and subsequent analysis by means of NMR spectroscopy.
[0128] The yield of phenyl isocyanate was 68% with a selectivity of
69%.
Example 6: Conversion of Methyl N-Phenylcarbamate into Phenyl
Isocyanate by Cleavage at 200.degree. C. in the Presence of Sodium
3-Sulfobenzenesulfonate (Catalyst of Type (C)) at a Molar Ratio of
Carbamate to Catalyst of 1.01:1
[0129] In an inertized multi-neck flask, 0.50 g (2.81 mmol) of
phenanthrene and also 9.99 g (26.26 mmol) of sodium
3-sulfobenzenesulfonate were suspended in 25.02 g (146.99 mmol) of
diphenyl ether. The reaction mixture was heated to 215.degree. C.
In an inertized Schlenk tube, 4.01 g (26.53 mmol) of methyl
N-phenylcarbamate were heated to 150.degree. C. Completely
transferring the methyl N-phenylcarbamate into the reaction mixture
resulted in a mixture having a temperature of 200.degree. C. This
temperature was held constant for 120 minutes. The gaseous reaction
products formed were driven out at an argon inert gas flow of 10
l/h and collected in a cold trap. The progress of the reaction was
monitored by means of continuous sampling from the reaction vessel
and subsequent analysis by means of NMR spectroscopy.
[0130] The yield of phenyl isocyanate was 69% with a selectivity of
81%.
Example 7: Conversion of Methyl N-Phenylcarbamate into Phenyl
Isocyanate by Cleavage at 200.degree. C. in the Presence of
N,N'-Diphenylformamidine (Catalyst of Type (A)) at a Molar Ratio of
Carbamate to Catalyst of 19.1:1
[0131] In an inertized multi-neck flask, 0.81 g (4.54 mmol) of
phenanthrene and also 0.44 g (2.24 mmol) of
N,N'-diphenylformamidine were dissolved in 25.35 g (148.93 mmol) of
diphenyl ether. The reaction mixture was heated to 216.degree. C.
In an inertized Schlenk tube, 6.48 g (42.87 mmol) of methyl
N-phenylcarbamate were heated to 150.degree. C. Completely
transferring the methyl N-phenylcarbamate into the reaction mixture
resulted in a mixture having a temperature of 200.degree. C. This
temperature was held constant for 120 minutes. The gaseous reaction
products formed were driven out at an argon inert gas flow of 10
l/h and collected in a cold trap. The progress of the reaction was
monitored by means of continuous sampling from the reaction vessel
and subsequent analysis by means of NMR spectroscopy.
[0132] The yield of phenyl isocyanate was 32% with a selectivity of
84%.
Example 8: Conversion of Dimethyl Toluene-2,4-Dicarbamate into
Toluene 2,4-Diisocyanate by Cleavage at 200.degree. C. in the
Presence of Sodium 3-Sulfobenzenesulfonate (Catalyst of Type (C))
at a Molar Ratio of Carbamate to Catalyst of 10.1:1
[0133] In an inertized multi-neck flask, 0.62 g (3.48 mmol) of
phenanthrene and also 1.27 g (3.34 mmol) of sodium
3-sulfobenzenesulfonate were suspended in 30.42 g (178.72 mmol) of
diphenyl ether. To the reaction mixture were added 8.02 g (33.66
mmol) of dimethyl toluene-2,4-dicarbamate and the mixture was
heated to 200.degree. C. This temperature was held constant for 120
minutes. The gaseous reaction products formed were driven out at an
argon inert gas flow of 10 l/h and collected in a cold trap. The
progress of the reaction was monitored by means of continuous
sampling from the reaction vessel and subsequent analysis by means
of .sup.1H NMR spectroscopy.
[0134] The yield of toluene 2,4-diisocyanate was 50% with a
selectivity of 86%.
Example 9: Conversion of Methyl N-Octylcarbamate into n-Octyl
Isocyanate by Cleavage at 200.degree. C. in the Presence of Sodium
3-Sulfobenzenesulfonate (Catalyst of Type (C)) at a Molar Ratio of
Carbamate to Catalyst of 19.5:1
[0135] In an inertized multi-neck flask, 0.49 g (2.75 mmol) of
phenanthrene and also 0.52 g (1.37 mmol) of sodium
3-sulfobenzenesulfonate were suspended in 25.30 g (148.64 mmol) of
diphenyl ether. The reaction mixture was heated to 215.degree. C.
In an inertized Schlenk tube, 5.00 g (26.70 mmol) of methyl
N-octylcarbamate were heated to 150.degree. C. Completely
transferring the methyl N-octylcarbamate into the reaction mixture
resulted in a mixture having a temperature of 200.degree. C. This
temperature was held constant for 120 minutes. The gaseous reaction
products formed were driven out at an argon inert gas flow of 10
l/h and collected in a cold trap. The progress of the reaction was
monitored by means of continuous sampling from the reaction vessel
and subsequent analysis by means of NMR spectroscopy.
[0136] The yield of n-octyl isocyanate was 31% with a selectivity
of 84%.
Example 10: Conversion of Methyl N-Phenylcarbamate into Phenyl
Isocyanate by Cleavage at 200.degree. C. in the Presence of
Tropolone (Catalyst of Type (B)) at a Molar Ratio of Carbamate to
Catalyst of 18.0:1
[0137] In an inertized multi-neck flask, 0.60 g (3.37 mmol) of
phenanthrene and also 0.23 g (1.88 mmol) of tropolone were
dissolved in 25.78 g (151.46 mmol) of diphenyl ether. The reaction
mixture was heated to 215.degree. C. In an inertized Schlenk tube,
5.11 g (33.80 mmol) of methyl N-phenylcarbamate were heated to
150.degree. C. Completely transferring the methyl N-phenylcarbamate
into the reaction mixture resulted in a mixture having a
temperature of 200.degree. C. This temperature was held constant
for 120 minutes. The gaseous reaction products formed were driven
out at an argon inert gas flow of 101/h and collected in a cold
trap. The progress of the reaction was monitored by means of
continuous sampling from the reaction vessel and subsequent
analysis by means of NMR spectroscopy.
[0138] The yield of phenyl isocyanate was 19% with a selectivity of
86%.
Example 11: Conversion of Methyl N-Phenylcarbamate into Phenyl
Isocyanate by Cleavage at 200.degree. C. in the Presence of
Triazabicyclodecene at a Molar Ratio of Carbamate to Catalyst of
18.5:1 (Comparative Example Using a Catalyst with an Excessively
Low pK.sub.B)
[0139] In an inertized multi-neck flask, 0.75 g (4.21 mmol) of
phenanthrene and also 0.31 g (2.23 mmol) of
3,4,6,7,8,9-hexahydro-2H-pyrimido[1,2-a]pyrimidine
(triazabicyclodecene, TBD, pK.sub.B=-0.47) were dissolved in 30.02
g (176.37 mmol) of diphenyl ether. The reaction mixture was heated
to 215.degree. C. In an inertized Schlenk tube, 6.25 g (41.34 mmol)
of methyl N-phenylcarbamate were heated to 150.degree. C.
Completely transferring the methyl N-phenylcarbamate into the
reaction mixture resulted in a mixture having a temperature of
200.degree. C. This temperature was held constant for 120 minutes.
The gaseous reaction products formed were driven out at an argon
inert gas flow of 101/h and collected in a cold trap. The progress
of the reaction was monitored by means of continuous sampling from
the reaction vessel and subsequent analysis by means of NMR
spectroscopy.
[0140] The yield of phenyl isocyanate was 2% with a selectivity of
2%.
Example 12: Conversion of Methyl N-Phenylcarbamate into Phenyl
Isocyanate by Cleavage at 200.degree. C. in the Presence of Sodium
Hydrogensulfate (Catalyst of Type (C)) at a Molar Ratio of
Carbamate to Catalyst of 18.3:1
[0141] In an inertized multi-neck flask, 0.63 g (3.53 mmol) of
phenanthrene and also 0.22 g (1.83 mmol) of sodium hydrogensulfate
were dissolved in 30.64 g (180.16 mmol) of diphenyl ether. The
reaction mixture was heated to 215.degree. C. In an inertized
Schlenk tube, 5.07 g (33.56 mmol) of methyl N-phenylcarbamate were
heated to 150.degree. C. Completely transferring the methyl
N-phenylcarbamate into the reaction mixture resulted in a mixture
having a temperature of 200.degree. C. This temperature was held
constant for 120 minutes. The gaseous reaction products formed were
driven out at an argon inert gas flow of 10 l/h and collected in a
cold trap. The progress of the reaction was monitored by means of
continuous sampling from the reaction vessel and subsequent
analysis by means of .sup.1H NMR spectroscopy.
[0142] The yield of phenyl isocyanate was 42% with a selectivity of
90%.
Example 13: Conversion of Methyl N-Phenylcarbamate into Phenyl
Isocyanate by Cleavage at 200.degree. C. in the Presence of Sodium
Sulfate at a Molar Ratio of Carbamate to Catalyst of 19.3:1
(Comparative Example to Example 12)
[0143] In an inertized multi-neck flask, 0.59 g (3.31 mmol) of
phenanthrene and also 0.25 g (1.76 mmol) of sodium sulfate were
dissolved in 30.17 g (177.25 mmol) of diphenyl ether. The reaction
mixture was heated to 216.degree. C. In an inertized Schlenk tube,
5.13 g (33.96 mmol) of methyl N-phenylcarbamate were heated to
150.degree. C. Completely transferring the methyl N-phenylcarbamate
into the reaction mixture resulted in a mixture having a
temperature of 200.degree. C. This temperature was held constant
for 120 minutes. The gaseous reaction products formed were driven
out at an argon inert gas flow of 10 l/h and collected in a cold
trap. The progress of the reaction was monitored by means of
continuous sampling from the reaction vessel and subsequent
analysis by means of .sup.1H NMR spectroscopy.
[0144] The yield of phenyl isocyanate was 17% with a selectivity of
92%.
Example 14: Conversion of Methyl N-Phenylcarbamate into Phenyl
Isocyanate by Cleavage at 200.degree. C. in the Presence of
Sulfuric Acid at a Molar Ratio of Carbamate to Catalyst of 19.1:1
(Comparative Example to Example 12)
[0145] In an inertized multi-neck flask, 0.62 g (3.48 mmol) of
phenanthrene and also 0.17 g (1.73 mmol) of sulfuric acid were
dissolved in 30.44 g (178.83 mmol) of diphenyl ether. The reaction
mixture was heated to 216.degree. C. In an inertized Schlenk tube,
4.99 g (33.03 mmol) of methyl N-phenylcarbamate were heated to
150.degree. C. Completely transferring the methyl N-phenylcarbamate
into the reaction mixture resulted in a mixture having a
temperature of 200.degree. C. This temperature was held constant
for 120 minutes. The gaseous reaction products formed were driven
out at an argon inert gas flow of 10 l/h and collected in a cold
trap. The progress of the reaction was monitored by means of
continuous sampling from the reaction vessel and subsequent
analysis by means of .sup.1H NMR spectroscopy.
[0146] The yield of phenyl isocyanate was 17% with a selectivity of
89%.
Example 15: Conversion of 4-Methoxyphenyl N-Phenylcarbamate into
Phenyl Isocyanate by Cleavage at 200.degree. C. in the Presence of
Sodium Hydrogensulfate (Catalyst of Type (C)) at a Molar Ratio of
Carbamate to Catalyst of 15.9:1
[0147] In an inertized multi-neck flask, 0.62 g (3.48 mmol) of
phenanthrene and also 0.25 g (2.08 mmol) of sodium hydrogensulfate
were dissolved in 29.95 g (175.96 mmol) of diphenyl ether. The
reaction mixture was heated to 215.degree. C. In an inertized
Schlenk tube, 8.05 g (33.09 mmol) of 4-methoxyphenyl
N-phenylcarbamate were heated to 150.degree. C. Completely
transferring the 4-methoxyphenyl N-phenylcarbamate into the
reaction mixture resulted in a mixture having a temperature of
200.degree. C. This temperature was held constant for 120 minutes.
The gaseous reaction products formed were driven out at an argon
inert gas flow of 10 l/h and collected in a cold trap. The progress
of the reaction was monitored by means of continuous sampling from
the reaction vessel and subsequent analysis by means of HPLC
chromatography.
[0148] The yield of phenyl isocyanate was 50% with a selectivity of
71%.
Example 16: Conversion of 4-Methoxyphenyl N-Phenylcarbamate into
Phenyl Isocyanate by Thermal Cleavage at 200.degree. C. in Diphenyl
Ether (Comparative Example to Example 15)
[0149] In an inertized multi-neck flask, 0.61 g (3.42 mmol) of
phenanthrene were dissolved in 30.10 g (176.84 mmol) of diphenyl
ether. The reaction mixture was heated to 215.degree. C. In an
inertized Schlenk tube, 8.03 g (33.01 mmol) of 4-methoxyphenyl
N-phenylcarbamate were heated to 150.degree. C. Completely
transferring the 4-methoxyphenyl N-phenylcarbamate into the
reaction mixture resulted in a mixture having a temperature of
200.degree. C. This temperature was held constant for 120 minutes.
The gaseous reaction products formed were driven out at an argon
inert gas flow of 10 l/h and collected in a cold trap. The progress
of the reaction was monitored by means of continuous sampling from
the reaction vessel and subsequent analysis by means of HPLC
chromatography.
[0150] The yield of phenyl isocyanate was 27% with a selectivity of
84%.
Example 17: Conversion of 4-Tert-Butylphenyl N-Phenylcarbamate into
Phenyl Isocyanate by Cleavage at 200.degree. C. in the Presence of
Sodium Hydrogensulfate (Catalyst of Type (C)) at a Molar Ratio of
Carbamate to Catalyst of 15.3:1
[0151] In an inertized multi-neck flask, 0.64 g (3.59 mmol) of
phenanthrene and also 0.26 g (2.17 mmol) of sodium hydrogensulfate
were dissolved in 30.16 g (177.19 mmol) of diphenyl ether. The
reaction mixture was heated to 215.degree. C. In an inertized
Schlenk tube, 8.94 g (33.19 mmol) of 4-tert-butylphenyl
N-phenylcarbamate were heated to 150.degree. C. Completely
transferring the 4-tert-butylphenyl N-phenylcarbamate into the
reaction mixture resulted in a mixture having a temperature of
200.degree. C. This temperature was held constant for 120 minutes.
The gaseous reaction products formed were driven out at an argon
inert gas flow of 10 l/h and collected in a cold trap. The progress
of the reaction was monitored by means of continuous sampling from
the reaction vessel and subsequent analysis by means of HPLC
chromatography.
[0152] The yield of phenyl isocyanate was 48% with a selectivity of
74%.
Example 18: Conversion of 4-Tert-Butylphenyl N-Phenylcarbamate into
Phenyl Isocyanate by Thermal Cleavage at 200.degree. C. in Diphenyl
Ether (Comparative Example to Example 17)
[0153] In an inertized multi-neck flask, 0.60 g (3.37 mmol) of
phenanthrene were dissolved in 31.26 g (183.67 mmol) of diphenyl
ether. The reaction mixture was heated to 215.degree. C. In an
inertized Schlenk tube, 8.76 g (32.52 mmol) of 4-tert-butylphenyl
N-phenylcarbamate were heated to 150.degree. C. Completely
transferring the 4-tert-butylphenyl N-phenylcarbamate into the
reaction mixture resulted in a mixture having a temperature of
200.degree. C. This temperature was held constant for 120 minutes.
The gaseous reaction products formed were driven out at an argon
inert gas flow of 10 l/h and collected in a cold trap. The progress
of the reaction was monitored by means of continuous sampling from
the reaction vessel and subsequent analysis by means of HPLC
chromatography.
[0154] The yield of phenyl isocyanate was 23% with a selectivity of
87%.
* * * * *