U.S. patent application number 09/750253 was filed with the patent office on 2002-02-14 for process for the recovery and recycle of d-tartaric acid.
This patent application is currently assigned to American Cyanamid Company. Invention is credited to Kremer, Kenneth Alfred Martin.
Application Number | 20020019567 09/750253 |
Document ID | / |
Family ID | 26869069 |
Filed Date | 2002-02-14 |
United States Patent
Application |
20020019567 |
Kind Code |
A1 |
Kremer, Kenneth Alfred
Martin |
February 14, 2002 |
Process for the recovery and recycle of D-tartaric acid
Abstract
There is provided a process for the recovery of essentially
enantiomerically pure D-tartaric acid from aqueous and organic
waste streams generated in the resolution of racemic
2-amino-2,3-dimethylbutyro- nitrile via the formation and isolation
of a crystalline monobasic tartrate salt. The recovered optically
pure D-tartaric acid may be efficiently recycled to provide a
sustainable resolution of racemic 2-amino-2,3-dimethylbutyro-
nitrile.
Inventors: |
Kremer, Kenneth Alfred Martin;
(Lawrenceville, NJ) |
Correspondence
Address: |
Susan Stetzel
Intellectual Property Department
BASF Corporation
3000Continental Drive - North
Mount Olive
NJ
07828-1234
US
|
Assignee: |
American Cyanamid Company
Madison
NJ
|
Family ID: |
26869069 |
Appl. No.: |
09/750253 |
Filed: |
December 28, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60173372 |
Dec 28, 1999 |
|
|
|
Current U.S.
Class: |
562/585 |
Current CPC
Class: |
C07C 253/34 20130101;
C07C 51/412 20130101; C07C 51/43 20130101; C07C 59/255 20130101;
C07C 255/24 20130101; C07C 59/255 20130101; C07C 59/255 20130101;
C07C 51/43 20130101; C07C 253/34 20130101; C07C 51/02 20130101;
C07C 51/412 20130101; C07C 51/02 20130101 |
Class at
Publication: |
562/585 |
International
Class: |
C07C 059/255 |
Claims
What is claimed is:
1. A process for the recovery of essentially enantiomerically pure
D-tartaric acid from a waste stream containing D-tartrate salts
which comprises acidifying said waste stream to a pH of about 2.5
to 4.5 to obtain a crystalline alkali metal hydrogen D-tartrate;
and reacting said alkali metal hydrogen D-tartrate with at least
one molar equivalent of an acid, optionally in the presence of a
solvent.
2. The process according to claim 1 wherein the alkali metal is
sodium or potassium.
3. The process according to claim 1 wherein the acid is a mineral
acid.
4. The process according to claim 3 wherein the acid is
hydrochloric acid or sulfuric acid.
5. The process according to claim 1 wherein the solvent is methanol
or ethanol.
6. The process according to claim 4 wherein the solvent is
ethanol.
7. The process according to claim 1 wherein the D-tartrate salt is
disodium D-tartrate, dipotassium D-tartrate, ammonium D-tartrate or
a mixture thereof.
8. The process according to claim 1 wherein the alkali metal
hydrogen D-tartrate is reacted with one molar equivalent of
acid.
9. The process according to claim 1 wherein the pH is about 3.0 to
4.0.
10. The process according to claim 9 wherein the pH is about
3.0.
11. A process for the continuous resolution of racemic
2-amino-2,3-dimethylbutyronitrile having D-tartaric acid as
resolving agent which comprises the following steps: a) reacting
racemic 2-amino-2,3-dimethylbutyronitrile with D-tartaric acid in
the presence of C.sub.1-C.sub.4alkanol to give the crystalline
D-tartrate salt of (R)-2-amino-2,3-dimethylbutyronitrile and a
first waste stream; b) reacting said D-tartrate salt with an alkali
metal hydroxide in the presence of water and a water-immiscible
solvent to give (R)-2-amino-2,3-dimethylbutyronitrile and a second
waste stream; c) acidifying said first and second waste streams to
a pH of about 2.5 to 4.5 to form a crystalline alkali metal
hydrogen D-tartrate salt; d) reacting said hydrogen D-tartrate salt
with at least one molar equivalent of an acid, optionally in the
presence of a solvent to give essentially enantiomerically pure
D-tartaric acid; and e) reacting said D-tartaric acid according to
steps a through d.
12. The process according to claim 11 wherein the pH in step c is
about 3.0 to 4.0.
13. The process according to claim 11 wherein the water-immiscible
solvent in step b is toluene.
14. The process according to claim 11 wherein the solvent in step d
is an aliphatic alkanol.
15. The process according to claim 11 wherein the
C.sub.1-C.sub.4alkanol is methanol.
Description
BACKGROUND OF THE INVENTION
[0001] Imidazolinone compounds, for instance, those described in
U.S. Pat. No. 4,188,487; No. 4,798,619 and No. 5,334,576, are
highly potent, broad spectrum, environmentally benign, herbicidal
agents. In general, the herbicidal activity of the R-isomer is
approximately 1.8 times that of the racemic imidazolinone compound.
Stereospecific processes to prepare chiral imidazolinone herbicidal
agents, either directly or indirectly, from
(R)2-amino-2,3-dimethylbutyronitrile are described in U.S. Pat. No.
4,683,324 and co-pending patent application Ser. No. 09/304,401,
filed on May 3, 1999.
[0002] Said nitrile is prepared by a two-step resolution of racemic
2-amino-2,3-dimethylbutyronitrile using D-(-)-tartaric acid as the
resolving agent. D-tartatic acid does not occur in abundance in
nature, and methods for its production are limited. Although
D-tartaric acid is commmercially available, it is expensive and is
only available in limited quantities.
[0003] Therefore, it is an object of the present invention to
provide a process for the recovery of D-tartaric acid from the
two-step resolution of racemic
2-amino-2,3-dimethylbutyronitrile.
[0004] It is another object of this invention to provide a process
for the recycle of said recovered D-tartaric acid in the resolution
process.
[0005] It is a feature of this invention that the processes
provided thereby may be used for repeated recovery and reuse of
D-tartaric acid in said two-step resolution.
SUMMARY OF THE INVENTION
[0006] The present invention provides a process for the recovery of
essentially enantiomerically pure D-tartaric acid from a waste
stream containing D-tartrate salts which comprises acidifying said
waste stream to a pH of about 2.5 to 4.5 to obtain a crystalline
alkali metal hydrogen D-tartrate; and reacting said alkali metal
hydrogen D-tartrate with an acid, optionally in the presence of a
solvent.
[0007] The present invention also provides a process for the
recycle of recovered D-tartaric acid in the continuous resolution
of racemic 2-amino-2,3-dimethyl-butyronitrile.
DETAILED DESCRIPTION OF THE INVENTION
[0008] Imidazolinone compounds such as those described in U.S. Pat.
No. 4,188,487, No. 4,798,619 and No. 5,334,576 are highly potent,
broad spectrum, environmentally benign, herbicidal agents. Chiral
imidazolinone compounds having the (R) configuration demonstrate an
increase in herbicidal activity over the corresponding racemic
mixture. The preparation of said chiral compounds by the resolution
of racemic 2-amino-2,3-dimethylbutyronitrile, hydrolysis of the
resultant (R) 2-amino-2,3-dimethyl-butyronitrile to the
corresponding (R)2-amino-2,3-dimethylbutyramide intermediate, and
subsequent elaboration of this intermediate to the (R)imidazolinone
herbicidal product is described in U.S. Pat. No. 4,683,324. The
preparation of chiral imidazolinone compounds having substantially
complete retention of enantiomeric purity directly from the
(R)aminonitrile starting material to the final chiral imidazolinone
herbicidal product is described in co-pending patent application
Ser. No. 09/304,401, filed on May 3, 1999.
[0009] In general, the two-step resolution described comprises a
first resolution step in which racemic
2-amino-2,3-dimethylbutyronitrile (II) in C.sub.1-C.sub.4alkanol is
treated with D-tartaric acid (I) to afford the D-tartrate salt of
(R)2-amino-2,4-dimethylbutyronitrile (III), which crystallizes from
solution. Because said aminonitrile partially decomposes in the
process of this kinetic resolution, the methanol mother liquor
contains varying amounts of ammonium D-tartrate (IV), which is
ordinarily discarded. This first resolution step is shown in Flow
Diagram I wherein the C.sub.1-C.sub.4alkanol is methanol. 1
[0010] In the second resolution step,
(R)2-amino-2,3-dimethylbutyronitrile (VI) is liberated from its
D-tartrate salt (III) by treatment with an alkali metal hydroxide
in the presence of a minimum amount of water and a water-immiscible
solvent, such as toluene. This second resolution step yields an
aqueous phase containing a full equivalent of the di(alkali metal)
salt of D-tartaric acid (V), which is also ordinarily discarded.
This second resolution step is illustrated in flow diagram II
wherein M is an alkali metal and the water immiscible solvent is
toluene. 2
[0011] Thus both resolution steps give rise to waste streams
containing D-tartrate salts.
[0012] Although L-tartaric acid is natural tartaric acid which
occurs widely in nature, either as the free acid or in combination
with potassium, calcium or magnesium, D-tartaric acid does not
occur widely in nature and is commercially available only in
limited quantities. Further, existing methods for producing
D-tartaric acid are limited. Surprisingly, it has now been found
that D-tartaric acid may be recovered in high yield and in
essentially enantiomerically pure form from the waste streams
produced in the resolution of racemic
2-amino-2,3-dimethylbutyronitrile. Advantageously, the recovered
D-tartaric acid may be recycled for use in the same resolution of
said aminonitrile. Beneficially, the processes of this invention
may be run repetitively, i.e., D-tartaric acid may be repeatedly
recovered and recycled in a continuous resolution of racemic
2-amino-2,3-dimethylbutyronitrile, allowing for a sustainable
resolution process.
[0013] In accordance with the process of the invention the
di(alkali metal) D-tartrate or ammonium D-tartrate waste streams
produced in the resolution of the above-said aminonitrile are
acidified to a pH of about 2.5 to 4.5, preferably 3.0 to 4.0, most
preferably about 3.0. The acidification is preferably conducted
with hydrochloric or sulfuric acid, to form the crystalline
mono-basic hydrogen D-tartrate (VII) and said hydrogen D-tartrate
is treated with at least one molar equivalent of an acid,
optionally in the presence of a solvent, preferably an aliphatic
alkanol, more preferably methanol or ethanol, to give essentially
enantiomerically pure D-tartarc acid (I). The process of the
invention is illustrated in flow diagram III wherein M is an alkali
metal. 3
[0014] The recovered D-tartaric acid (I) may then be utilized
directly in the first resolution step by adding the recovered
D-tartaric acid to a solution of racemic
2-amino-2,4-dimethylbutyronitrile in a water-immiscible solvent,
such as toluene, to yield the corresponding D-tartrate salt (III)
as shown hereinabove in flow diagram I.
[0015] It is also intended that the processes of this invention
embrace the recovery and recycle of L-tartaric acid in a resolution
of racemic 2-amino-2,3-dimethyl-butyronitrile to produce
(S)2-amino-2,3-dimethylbuty- ro-nitrile, such as that described in
U.S. Pat. No. 4,683,324.
[0016] Acids suitable for use in the process of the invention
include mineral acids such as hydrogen halides, sulfuric acid,
phosphoric acid, or the like, preferably hydrochloric acid or
sulfuric acid.
[0017] Solvents suitable for use in the inventive process include
polar solvents, preferably water miscible. Preferable solvents
include aliphatic alkanols such as methanol, ethanol, propanol,
isopropanol, or the like, preferably methanol or ethanol, more
preferably ethanol.
[0018] Alkali metals include sodium, potassium, or lithium,
preferably sodium or postassium.
[0019] In general, reaction temperatures for the inventive process
are directly related to reaction rate, that is increased reaction
temperature leads to increased reaction rate. However, excessively
high reaction temperatures are to be avoided. Suitable reaction
temperatures may be about 0.degree. C. to 50.degree. C., preferably
about 5.degree. C. to 35.degree. C., more preferably about
10.degree. to 30.degree. C.
[0020] In actual practice, waste streams from a 2-step resolution
of racemic 2-amino-2,3-dimethylbutyronitrile, combined or
individually, are acidified to a pH of about 3 to form crystalline
alkali metal hydrogen D-tartrate and said hydrogen D-tartrate is
reacted with at least one molar equivalent of acid, preferably
hydrochloric acid or sulfuric acid, optionally in the presence of a
solvent, preferably an aliphatic alkanol, more preferably methanol
or ethanol, to give the desired essentially enantiomerically pure
D-tartartic acid. Advantageously, the crystalline alkali metal
hydrogen D-tartrate may be isolated using conventional means such
as filtration or, alternatively, may be carried on in the inventive
process as is or as a concentrated slurry. Similarly, the recovered
D-tartaric acid may be isolated using conventional techniques or
recycled as is or as a concentrated slurry.
[0021] In order to facilitate a further understanding of the
invention, the following examples are presented primarily for the
purpose of illustrating certain more specific details thereof. The
invention is not to be deemed limited thereby except as defined in
the claims. HPLC designates high performance liquid chromatography.
Unless otherwise indicated, all parts are parts by weight.
EXAMPLE 1
[0022] Recovery of D-sodium Hydrogen Tartrate from Aqueous Disodium
Tartrate Waste 4
[0023] A mixture of (R)-2-amino-2,3-dimethylbutyronitrile
(2S,3S)-tartaric acid salt (89.9 g, 0.34 mmole), toluene, ice and
50% sodium hydroxide (68.5 g, 0.85 mmol) is shaken until no solid
particles are observed. The phases are separated and the aqueous
disodium tartrate waste produced (343.3 g, 15 wt % D-tartaric acid)
is acidified to a pH of about 3 with concentrated hydrochloric acid
over a 30 minute period at 8-13.degree. C., stirred for 15 minutes
and filtered. The filtercake is washed with methanol and dried in
vacuo to afford recovered D-sodium hydrogen tartrate as an
off-white solid 53.2 g (91% recovery) in >99% purity and 100%
optical purity as determined by HPLC analysis.
[0024] Using essentially the same procedure and employing
concentrated sulfuric acid in place of concentrated hydrochloric
acid, recovered D-sodium hydrogen tartrate is obtained as an
off-white solid (279 g, 77% recovery) >99% purity and 100%
optical purity as determined by HPLC analysis.
EXAMPLE 2
[0025] Recovery of D-sodium Hydrogen Tartrate from Combined Aqueous
Disodium Tartrate and Methanolic Ammonium Tartrate Waste 5
[0026] A mixture of aqueous disodium tartrate waste produced as
described in Example 1 (438.5 g, 14.5 wt % D-tartaric acid) and a
methanolic mother liquor waste slurry of ammonium tartrate (278 g,
2.6 wt % D-tartaric acid) produced as described in U.S. Pat. No.
4,683,324 is acidified to a pH of about 3 with concentrated
hydrochloric acid over a 30 minute period at room temperature,
stirred for 25 minutes and filtered. The filtercake is washed with
methanol and dried in vacuo to afford recovered D-sodium hydrogen
tartrate as an off-white solid, 73.7 g, (92% recovery) in >99%
purity and 100% optical purity as determined by HPLC analysis.
EXAMPLE 3
[0027] Preparation of (R)-2-Amino-2,3-dimethylbutyronitrile
(2S,3S)-tartrate from Recovered D-sodium Hydrogen Tartrate 6
[0028] A slurry of recovered D-sodium hydrogen tartrate (20.6 g,
0.119 mol) in methanol is treated with concentrated sulfuric acid
(6.1 g, 0.059 mol) at room temperature, stirred for one hour and
filtered to remove inorganic salts. A portion of the filtrate is
concentrated in vacuo to give a solution of recovered D-tartaric
acid (13.6 g, 0.090 mol, 82%) in methanol. This solution is treated
with a solution of racemic-2-amino-2,3-dimethylbutyronitrile (12.4
g, 0.11 mol) in toluene, stirred for 16 hours and filtered. The
filtercake is washed with methanol and dried to afford
(R)-2-amino-2,3-dimethylbutyronitrile (2S,3S)-tartrate, 22.3 g,
(61% yield) 95/5 R/S isomer ratio as determined by HPLC
analysis.
EXAMPLE 4
[0029] Preparation of Crystalline D-tartaric Acid from Recovered
D-sodium Hydrogen Tartrate in Ethanol 7
[0030] A slurry of recovered D-sodium hydrogen tartrate (50.5 g,
0.293 mol) in ethanol is treated with concentrated sulfuric acid
(15.0 g, 0.147 mol) at room temperature, stirred for 45 minutes and
filtered to remove inorganic salts. The filtrate is concentrated in
vacuo to afford a concentrated slurry of D-tartaric acid in
ethanol. The slurry is diluted with toluene and filtered. The
filtercake is washed with toluene and dried to afford D-tartaric
acid as a crystalline solid, 37.3 g, (83% yield) 97.7% purity 100%
optical purity as determined by HPLC analysis.
EXAMPLE 5
[0031] Recovery of D-potassium Hydrogen Tartrate from Aqueous
Dipotassium Tartrate Waste 8
[0032] Aqueous dipotassium tartrate waste (137.0, 14.7% wt %
D-tartaric acid) is acidified to a pH of about 3 with concentrated
hydrochloric acid over a 30 minute period at 13-28.degree. C.,
stirred for about 15 minutes and filtered. The filtercake is washed
with methanol and dried in vacuo to afford recovered D-potassium
hydrogen tartrate 24, 8 g, (98% recovery) in >99% purity as
determined by HPLC analysis.
EXAMPLE 6
[0033] Preparation of Crystalline D-tartaric Acid from Recovered
D-potassium Hydrogen Tartrate in Ethanol 9
[0034] A slurry of recovered D-potassium hydrogen tartrate (22.1 g,
0.117 mol) in ethanol (148 g) is treated with concentrated sulfuric
acid (6.0 g, 0.0588 mol) at room temperature, stirred for 45
minutes and filtered to remove inorganic salts. The filtrate is
concentrated in vacuo to a viscous slurry. The slurry is diluted
with acetonitrile and filtered. The filtercake is washed with
acetonitrile and dried to afford crystalline D-tartaric acid, 4.7
g, (25% recovery), 92.3% purity as determined by HPLC analysis.
* * * * *