The present invention relates to an a commercially viable process for the
preparation of 2-amino cyanoacetamide of formula (I)
(I)
which is a useful pharmaceutical intermediate for preparing Temozolomide
API useful in the treatment of cancer.
The process according to the present invention results in highly pure
material, which is desirable to produce a high pure API.
BACKGROUND OF THE INVENTION
2-amino-2-cyanoacetamide also known as Amino cyanoacetamide and has
the following structure:
Aminocyanacetamide is an interesting intermediate for the production of
imidazoles, pyrazines, purines or pteridines.
Milleret et al. in J. Am. Chem. Soc. 74, 2892-2894 (1952) discloses a
process for production of aminocyanacetamide by reaction of cyanoacetamide in
aqueous acetic acid and subsequent reduction of the nitrosocyanacetamide with
Raney nickel to give aminocyanacetamide.
Scheme 1: Process as per J. Am. Chem. Soc. 74, 2892-2894 (1952)
3
When nitrosating in aqueous acetic acid, large amounts of by-products are
formed and with sodium acetate, this produces the undesirable, very fine semisodium salt, which crystallizes with uncontrollable exothermic energy. The
subsequent reduction with Raney nickel shows strong tendencies towards over
hydration with the formation of a whole range of by-products.
Taylor et al. in J. Am. Chem. Soc., 76, 6080-6084 (1954) discloses the
process for the preparation of amino cyanacetamide starting from hydroxyimino
cyanacetamide, by hydrogenation with aluminum amalgam.
Scheme 2: Process as per J. Am. Chem. Soc., 76, 6080-6084 (1954)
This method can no longer be used for a technical application in view of the
problems associated with the waste disposal of the mercury catalyst. According to
the reference direct amalgamation of aminocyanoacetamide gives a very low yield
of 59%
Hans P Mettler et al. in US5003099 discloses the process for the preparation
of amino cyanacetamide, starting from cyanacetic acid esters or aminocyanacetic
esters in which the aminocyanacetamide by nitrosation of a cyanoacetic ester in
presence of an alkali nitrite, followed by hydrogenation of the resulting
hydroxyiminocyanacetic acid esters with platinum / hydrogen and subsequent
release of aminocyanacetamide with aqueous ammonia.
Scheme 3: Process as per US5003099
4
Hans Rudolf Miller et al. in US6194600 discloses the preparation method
of aminocyanoacetamide starting from cyanoacetamide.
Cyanoacetamide is nitrosylated with nitrites to form
nitrosocyanoacetamide, which is catalytically hydrogenated using precious metal
catalyst under H2 gas pressure upto 2 bar to form aminocyanoacetamide.
Scheme 4: Process as per US6194600
The process become commercially non- viable since it depends on used
precious metal catalyst and their recyclability besides lower yields.
It is an object of the present invention to overcome the associated
disadvantages in the above mentioned methods like having the low yields, costly
on an industrial scale, usages of the mercury catalyst or precious metal, problem for
the disposal of the salt wastes.
The process of the present invention provides a process for the production
of 2-amino cyanoacetamide having the purity exceeding 99.0% by HPLC and in
higher yields.
SUMMARY OF THE INVENTION
Particular aspects of the present invention relates to a process for the
preparation of 2-amino cyanoacetamide of formula (I)
5
(I)
Different aspects of the present application are summarized herein below.
In one aspect of the present application, the present invention relates to a
process for preparation of 2-amino cyanoacetamide (I),
(I)
comprising the steps of
a) reacting alkyl 2-cyanoacetate with sodium nitrite in presence of organic
acid and aqueous solvent at temperature ranging between 0-25°C to get
compound of formula (B);
b) reacting compound of formula (B) in aqueous solvent medium in the
presence 10 % w/w sodium bicarbonate aqueous solution added slowly at
temperature not exceeding 30°C followed by slow addition of sodium
dithionate or sodium sulphide to get un-isolated compound (C) ;
c) extracting the compound of formula (C) with dichloromethane solvent;
6
d) dry the solvent containing compound of formula (C) with brine solution or
sodium sulphate bed;
e) recover the solvent completely under vacuum below 35°C;
f) add methanol and cool the reaction mass upto temperature ranging between
-5 to +5°C;
g) reacting compound of formula (C) in step f) with methanolic ammonia at a
temperature ranging between -5 to +5°C for a time duration ranging between
30-120 min;
h) isolating the 2-amino cyanoacetamide of formula (I).
In yet another aspect the present invention also relates to the preparation of
2-amino cyanoacetamide having high purity exceeding 99.0 % by HPLC.
Further specific aspects of the present invention are detailed in the
description part of the specification, wherever appropriate.
DETAILED DESCRIPTION
As set forth herein, embodiments of the present invention provide a process
for preparation of 2-amino cyanoacetamide of formula (I).
The present invention provides a simple and industrially amenable process
for making the compound of formula (I), which exhibits various advantages over
other processes reported in the state of arts. The advantages are discussed on the
relevant places of further description. Individual embodiments of the present
invention are detailed herein below separately.
In one embodiment according to the present application, it provides a
process for the preparation of 2-amino cyanoacetamide of formula (I)
7
(I)
comprising the steps of:
a) reacting alkyl 2-cyanoacetate with sodium nitrite in presence of organic
acid and aqueous solvent at temperature ranging between 0-25°C to get
compound of formula (B);
b) reacting compound of formula (B) in aqueous solvent medium in
the presence 10 % w/w sodium bicarbonate aqueous solution added slowly
at temperature not exceeding 30°C followed by slow addition of sodium
dithionate or sodium sulphide to get un-isolated compound (C);
c) extracting the compound of formula (C) with dichloromethane solvent;
d) dry the solvent containing compound of formula (C) with brine solution or
sodium sulphate bed;
e) recover the solvent completely under vacuum below 35°C;
f) add methanol and cool the reaction mass upto temperature ranging between
-5 to +5°C;
g) reacting compound of formula (C) in step f) with methanolic ammonia at
a temperature ranging between -5 to +5°C for a time duration ranging between 30-
120 min;
8
h) isolating the 2-amino cyano acetamide of formula (I).
Individual steps of the embodiments are detailed herein below.
According to the present invention in step a) of the process for the
preparation of 2-amino cyanoacetamide, wherein R is an alkyl group having carbon
from C1-C4 in key starting materials alkyl 2-Cyanoacetate.
In a particular embodiment for the preparation of 2-amino cyano acetamide
in reaction of step a) the alkyl group as R is used as C2 alkane i.e. ethyl i.e. key
starting materials ethyl 2-Cyanoacetate, however, methyl-2-cyanoacetate or
isopropyl 2-cyanoacetate or n-butyl cyanoacetate may also be utilized suitably or
alternatively.
The organic acid used in the reaction of step a) are selected from formic
acid, acetic acid or propanoic acid and aqueous solvent is selected from water or
mixture with alcoholic solvent (C1-C3).
In a particular embodiment, the organic acid used in the reaction of step a)
is acetic acid.
Extraction in process step a) is carried out in presence of ethyl acetate or
toluene solvent and recovering the solvent followed by residue precipitation with
hydrocarbon solvent.
The process of the extraction may be performed in 2-5 times for the
residence time duration of at least about 15 minutes to ensure extraction
maximization.
The hydrocarbon solvent for precipitation may be selected from
cyclohexane or cycloheptane and more particularly it is cyclohexane.
The yield and purities obtained for compound of formula (B) were found to
be more than 90%w/w and 98% respectively.
9
The reacting of compound of formula (B) in aqueous solvent medium in the
presence 10 % w/w sodium bicarbonate aqueous solution added slowly at
temperature not exceeding 30°C followed by slow addition of sodium dithionate or
sodium sulphide to get un-isolated compound (C).
The addition of 10-14 % w/w sodium bicarbonate aqueous solution was
desirable to be slow, since the step was observed exothermic and temperature if
exceeded above 30°C may lead to degradation of compound of formula (B), which
has resulted in lower yields in subsequent steps.
Inventors of present application also observed that a lower quantity of
reducing agent may also result in poor yields. The preferred reducing agent used in
the step b) sodium dithionate or sodium sulphide, which is not only economically
viable but also make reaction conditions at room temperature and no pressure.
A preferred molar ratio of reducing agent- sodium dithionate or sodium
sulphide was found to be about 2-3 moles with respect to (w.r.t.) compound of
formula (B).
Inventors observed that addition of reducing agent- sodium dithionate or
sodium sulphide was desirable to be added in lots (being exothermic step), which
may be 2-5 equally divided lots in terms of weights while maintaining the room
temperature conditions of reaction.
Once the reaction is over, the extracting of the compound of formula (C)
with dichloromethane solvent was performed at room temperature, followed by
drying the solvent containing compound of formula (C) with brine solution or
sodium sulphate bed by conventional methods.
In a particular preferred embodiment according to the present process of
step c); 4 times extraction was performed in MDC for duration of 30 minutes at 25-
30ºC.
The recovery of the solvent was performed completely under vacuum below
35°C, since elevated temperatures were found harmful to the compound. In the
subsequent step, addition of methanol performed and cooled the reaction mass upto
temperature ranging between -5 to +5°C. In a particular embodiment, the addition
of methanol was done upto 1.0-1.5 times with respect to compound (B).
10
In another embodiment of the present application, the reacting of compound
of formula (C) in step f) is carried out with methanolic ammonia at a temperature
ranging between -5 to +5°C for a time duration ranging between 30-120 min. The
step is one of the key of the entire inventive process, since this step some time
observed to result in no product owing to hydrolysis with excess ammonia besides
other side products formation.
In the process of step g) of the present invention, the addition of methanolic
ammonia (10-14% w/w) was performed in quantities upto 2-2.8 times w/w with
respect to compound (C).
The addition of methanolic ammonia can be performed without isolation of
the compound of formula (C) to get the final compound of formula (I) i.e. insitu
reaction.
In a particular embodiment in step g), the addition of the 13% w/v
methanolic ammonia solution was used in about 60 minutes at a temperature
ranging between 0-5ºC.
The product can be isolated by suitable methods such as filtration, washing
with chilled methanol (2 times) and then dried.
In another embodiment of the present invention, it provides a highly pure 2-
aminocyano acetamide of formula (I) having purity exceeding 99.0% by HPLC.
The said highly pure compound 2-aminocyanoacetamide of formula (I) was
found to be an important or key intermediate in the synthesis of various active
pharmaceutical ingredients (APIs) viz, Temozolomide, which is an important
anticancer drug substance.
This highly pure 2-aminocyano acetamide of formula (I) provides overall
API cost more affordable to the patient in need.
While the present invention has been described in terms of its specific
embodiments, certain modifications and equivalents will be apparent to those
skilled in the art and are intended to be included within the scope of the present
invention.
11
Certain specific aspects and embodiments of the present application will be
explained in more detail with reference to the below examples, which are provided
by way for illustration purpose only and should not be construed as limiting the
scope of the invention in any manner.
EXAMPLES:
The following examples illustrate the nature of the invention and are
provided for illustrative purposes only and should not be construed to limit the
scope of the present invention.
The process of manufacturing 2-aminocyanoacetamide of formula (I)
comprises different steps, which are demonstrated as separate working examples.
Example 1: Preparation method of compound of formula (B), wherein R is
ethyl:
In a flask charged 2.5 lit. water, 369gm Sodium nitrite, 500gm Ethyl
Cyanoacetate. Stirred the reaction mass for 10 minutes at 25-30°Cand cool the
reaction mass upto 0-5°C under stirring. Slowly added 350gm acetic acid
maintaining 0-5°C. Maintain the reaction mixture at 0-5 °C for 15 minutes.
Raised the temperature of reaction mass to 20 to 25°C and maintain for 60
minutes.
Charged 750 ml Ethyl acetate into above reaction mixture and stirred for 45
minutes. Separate Aqueous and Organic layer and charged aqueous layer into RBF.
Repeated this extraction process for 2-4 times and combined all organic layers and
charged into RBF. Charged 375 ml NaHCO3 solution (10%w/w) into above
reaction mixture and stirred for 30 minutes at 25-30°C. Repeated the process 1-2
times. Separated the aqueous layer and combined all the organic layers. Charged
the organic layer into RBF and add 100gm sodium sulfate. Stirred reaction mixture
for 15 mins at 25-30°C. Filtered the dry organic layer, wash with 200ml of Ethyl
12
acetate and collect filtrate. Distilled the filtrate completely under vacuum at 40 to
45°C.
Charged 1500 ml cyclohexane into distilled residue and stirred for 45
minutes at 25-30°C. Filtered the above mixture and wash with 500 ml
cyclohexane. Dry the solid under vacuum at 40 to 45°C for 12hrs.
Output: 600gm; Yield (%w/w) = 95.5%w/w
Purity (By HPLC): 98.45% (area %)
Example 2: Preparation of crude 2-Aminocyano acetamide:
Charged 100 gm of (A) and 600 ml purified water into a flask at 25 to
30oC.Added saturated NaHCO3 solution (10% w/v) into above reaction mixture
through dropping funnel in 15 to 20 minutes at 25 to 30oC.Stirred the reaction mass
for 10 min at 25 to 30oC.
Charged 340gm of Sodium dithionite (85%) portion wise into the reaction
mixture in 30 to 45 minutes at 25 to 30oC. Stirred the reaction mass for 10 minutes at
25 to 30oC. Charged 400 ml methylene dichloride (MDC) into the reaction mixture
and stirred for 30 min at 25 to 30oC. Settle and separate aqueous and organic layer.
Repeated this process 4-5 times in the aqueous layer and combined all organic layers
and charged into the flask.
Charged 200 ml saturated NaCl solution.Stirred reaction mass for 30 min at
25 to 300C.Settled and separate aqueous and organic layer. Collect the organic
methylene dichloride (MDC) layer and distilled completely under vacuum at below
350C. Stripped out oily mass with 50 ml Methanol under vacuum at below 350C.
Charged 120 ml Methanol into the above reaction mass at 25 to 30oC.Cool
the reaction mixture ranging the temperature between 0 to 5
oC under stirring. Add
245 ml Methanolic ammonia (13%) solution into reaction mass at 0 to 5
oC in 60
minutes. Stirred reaction mixture 0 to 5o C for 30 minutes. Distilled out solvent from
reaction mass (upto 100 ml remain in the flask) under vacuum at 25 to 30oC. Cool the
13
reaction mass 0 to 5 oC and stirred for 30 minutes. Filter the reaction mass and washed
the solid with chilled methanol (60 ml x 2).Unload the wet cake and dry under
vacuum at 40 to 45oC.
Output =15gm;
Purity (By HPLC): 98.08% (area %)
Example 3: Preparation of crude 2-Aminocyanoacetamide:
Charged 100 gm of (B), and 600 ml purified water into a flask at 25 to
30oC. Added slowly saturated solution of NaHCO3 into above reaction mixture in
15 to 20 minutes at 25 to 30oC. Stirred the reaction mass for 10 min at a temperature
ranging between 25 to 30oC.
Charged 340gm Sodium dithionite (85%) portion wise into the reaction
mixture in 30 to 45 minutes at 25 to 30oC. Stirred the reaction mass for 10 min at 25
to 30oC. Charged 400 ml MDC into the reaction mixture and stirred for 30 min at 25
to 30oC. Settle and separate the aqueous and organic layer. Repeated this process 3-4
times in the aqueous layer and combined all organic layers and charged into the flask.
Charged 200 ml saturated NaCl solution. Stirred the reaction mass for 30
min at 25 to 300C. Settled and separate aqueous and organic layer. discard aqueous
layer, Collect MDC layer and distilled completely under vacuum at below
350C.Stripped out oily mass with 50 ml Methanol under vacuum at below 350C.
Charge 120 ml Toluene into above reaction mass at 25 to 300C. Cool the
reaction mixture 0 to 50C under stirring. Add 270 ml Methanolic ammonia (14± 1%)
solution into reaction mass at 0 to 50C in 60 minutes. Stirred the reaction mixture for
30 minutes. Filter the solid mass and washed with chilled methanol (60 ml x
2).Unload the wet cake and dried under vacuum at 35 to 400C for 12hrs.
Output = 15 gm;
Purity (By HPLC): 98.08% (area %)
14
Example 4: Preparation of crude 2-Aminocyano acetamide:
Charged 300 gm of (B), 48 gm Pt/C (50% wet), and 2400 ml methanol into
the 5lt Autoclave. Applied 6 - 7 kg hydrogen pressure under stirring. Raised the
temperature of reaction mass 35 to 40oC under stirring and maintain 6 to 7 kg H2
gas pressure for 8hr. Monitor reaction on TLC to check absence of compound of
(B). Cool the reaction mass 25 to 30oC. Unload reaction mixture and Filter through
hyflo and wash with 300 ml ethanol. Charged the filtrate into 5lt flask. Cool the
filtrate to 0oC and purged NH3 at below 30oC and monitor reaction on TLC to check
absence of (C) (in-situ). Concentrate reaction mixture under vacuum at 30 to 35oC
upto 800 ml remain in the flask. Cooled the residue at the temperature ranging
between 0 to 5oC and stirred for 1hr. Filter the reaction mixture and wash the cake
with 1000ml chilled methanol. Unload the wet cake and dry at 40 to 50oC for 12hr.
Output = 90gm;
Purity (By HPLC): 98.15% (area %)
Example 5: Purification of crude 2-Amino cyanoacetamide:
About 100gm of crude 2-Amino cyanoacetamide is charged in 1500 ml
methanol into RBF at room temperature. Raised the temperature of above reaction
mixture upto about 60 to 65oC. Stirred the reaction mixture for 30minutes and
charged 20gm activated charcoal under stirring and maintain the reaction mass for
30minutes. Filtered the reaction mass through hyflo bed at 60 to 65oC.Washed hyflo
bed with 140 ml hot methanol. Collected the filtrate and charged into another flask.
Cool reaction mass upto 0 to 5oC and stirred for 60 minutes at 0 to 5oC and filter.
Washed the solid recovered, with 100 ml methanol. Suck dry and unload wet cake.
Dry the material under vacuum at 40 to 45oC for about 10-12hrs.
15
Output: 65 gm; Yield (%w/w): 65% w/w
Purity (By HPLC): 99.19% (area %)
Example 6: Purification of crude 2-Aminocyanoacetamide:
Charged about 675 ml methanol in the flask and added 45 gm of crude
Aminocyanoacetamide at 25-30°C. Heat the reaction mass to 63-67°C and
maintained for about 30 min. Charged 9.0 gm charcoal under stirring and
maintained for about 30 min. Filtered hot solution through Hyflo bed and washed
with 60 ml hot methanol. Cool the filtrate upto 0-5°C and stirred for about 1 hr at
0-5°C.
Filtered the solid cake and washed with 45 ml chilled methanol. Suck dried
for about 60 min. Unload the crystalline material and dried under vacuum at 40-
45°C for 5 hrs.
Output: 40 gm; Yield (%w/w): 89% w/w
Purity (By HPLC): 99.25% (area %)
The above mentioned examples, which are provided by way of illustration,
should not be construed as limiting the scope of the invention with respect to
parameter/s, ingredient/s and quantities use etc.

We Claim:

1. A process for the preparation of 2-amino cyano acetamide of formula (I)
(I)
comprising the steps of :
a) reacting alkyl 2-cyanoacetate with sodium nitrite in presence of organic
acid and aqueous solvent at temperature ranging between 0-25°C to get compound
of formula (B);
b) reacting compound of formula (B) in aqueous solvent medium in the
presence 10 % w/w sodium bicarbonate aqueous solution added slowly at
temperature not exceeding 30°C followed by slow addition of sodium dithionate or
sodium sulphide to get un-isolated compound (C) ;
c) extracting the compound of formula (C) with dichloromethane solvent;
d) dry the solvent containing compound of formula (C) with brine solution or
sodium sulphate bed;
e) recover the solvent completely under vacuum below 35°C;
f) add methanol and cool the reaction mass upto temperature ranging between
-5 to +5°C ;
17
g) reacting compound of formula (C) in step f) with methanolic ammonia at
a temperature ranging between -5 to +5°C for a time duration ranging between 30-
120 min ;
h) isolating the 2-amino cyano acetamide of formula (I).
2. A process for the preparation of 2-amino cyano acetamide of formula (I)
according to claim 1, wherein alkyl group as R selected from C1-C4 alkane.
3. A process for the preparation of 2-amino cyano acetamide of formula (I) according
to claim 1, wherein reaction of step a) involving use of organic acid are selected
from formic acid, acetic acid or propanoic acid and aqueous solvent is selected from
water or mixture with alcoholic solvent (C1-C3).
4. A process for the preparation of 2-amino cyano acetamide of formula (I) according
to claim 1, wherein compound of formula (B) in step a) is isolated by extracting in
ethyl acetate or toluene solvent and recovering the solvent followed by residue
precipitation with hydrocarbon solvent.
5. A process for the preparation of 2-amino cyano acetamide of formula (I) according
to claim 1, wherein addition of methanol upto 1.2-1.5 times with respect to
compound (B) in the oily layer obtained in step e) of claim 1.
6. A process for the preparation of 2-amino cyano acetamide of formula (I) according
to claim 1, wherein addition of methanolic ammonia (10-14% w/w) in quantities
upto 2-2.8 times w/w with respect to compound (B) in step e) of claim 1.
18
7. A process according to claim 4, hydrocarbon solvent is selected from cyclohexane
or cycloheptane.
8. A highly pure 2-amino cyano acetamide of formula (I) according to the process of
claim-1 having purity exceeding 99.0 % by HPLC.