FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. Title of the invention. - PROCESS FOR THE PREPARATION OF DBMETHYLFORMAMIDE
DIMETHYLACETAL
2. Applicant(s)
(a) NAME: VIHITA CHEM PVT. LTD.
(b) NATIONALITY: INDIAN
(c) ADDRESS : 305, GIDC, ANKLESHWAR, 393002, GUJARAT, INDIA
3. PREAMBLE TO THE DESCRIPTION:
The following specification particularly describes the invention and the manner in which it is to be performed:

Field of the invention:
The present invention relates to improved process for the preparation of dimethylformamide dimethylacetal of formula (I). Dimethylformamide dimethylacetal of formula (I), which is an intermediate for the preparation of many pharmaceutical compounds. The invention also relates to the use of dimethylformamide dimethylacetal (I) for the preparation of pharmaceutical compounds.

Background of the invention:
Dimethylformamide dimethylacetal of formula (I) is a key intermediate for the preparation of many pharmaceutical compounds.
Journal of Heterocyclic Chemistry, Volume 46, Issue 5, pages 801-827 discloses the use of dimethylformamide dimethylacetal in the preparation of heterocyclic compounds via formylation of active methylene groups, methyl groups to give enamines, and formylation of amino groups to give amidines. These compounds are found to be useful intermediates in the formation and modification of heterocyclic compounds.
The synthesis of dimethylformamide dimethylacetamide is reported in JP patent 08277251, which involves treatment of dimethylformamide dimethyl sulfate adduct in the presence of MeONa in MeOH-hydrocarbon solvent mixtures, removing solid materials, followed by distillation of the filtrates. However, the usage of methanol and hydrochloride solvent at commercial scale should be avoided.

However, there is need to have a simple, commercially advantageous process for preparation of dimethylformamide dimethylacetal. Inventors of the present invention has found an improved process for the preparation of dimethylformamide dimethylacetal.
Object of the Invention:
The object of the present invention is to provide an improved process for the preparation of dimethylformamide dimethylacetal of formula (I).
Another object of the present invention is to provide a one stage process for the preparation of dimethylformamide dimethylacetal of formula (I), which is an intermediate for the preparation of many pharmaceutical compounds.
Yet another object of the preset invention is to provide the process for the preparation of dimethylformamide dimethylacetal with high purity.

Detailed Description of the invention:
The present invention provides an improved process for the preparation of dimethylformamide dimethylacetal of formula (I)

which comprise;
(a) reacting a dimethyl sulfate of formula (II) with N,N-dimethylformamide (III) in the presence or absent of a solvent at temperature in the range of 60°C to 120°C to obtain reaction mass;

(b) reacting the reaction mass with sodium methoxide; and
(c) isolating dimethylformamide dimethylacetamide of formula (I)
According to the embodiments of the present invention, the reaction of dimethyl sulfate with N,N-dimethylformamide is carried out in the presence of solvent or absent of solvent is carried out at 60°C to 120°C to obtain reaction mass .
The preferred solvent is alcohol selected from selected from methanol, ethanol, isopropanol, n-propanol, water or mixture therefore.

Preferably, the reaction is carried out at 80°C in the absence of solvent. The reaction of dimethylsulfate with N,N-dimethylformamide at 80°C provides reaction mass, which is an adduct of dimethylsulfate with N,N-dimethylformamide. After the completion of reaction, the reaction mass is cooled to room temperature.
The reaction mass formed as above is further added with sodium methoxide solution in Methanol. Preferably, sodium methoxide solution is prechilled to 0°C to 5°C before reaction.
After the addition of sodium methoxide, the reaction mass is maintained at 0°C to 5°C for about one hour and then temperature is increased to about 20-25°C and maintained for about one-two hours. The reaction mass is further heated to 60°C for about one hour and distilled to obtain the mixture of methanol and dimethylformamide dimethylacetal.
The dimethylformamide dimethylacetal is isolated from the mixture of methanol and dimethylformamide dimethylacetal by fraction distillation using column. Preferably, the mixture is undergone with fractional distillation using column. The preferred column is Vigreux column. The methanol is first distilled out about 60-65°C and then dimethylformamide dimethylacetal is isolated at about 80°C to 110°C.
According to the another aspect of the invention, there is provided high purity dimethylformamide dimethylacetal, which comprises reaction of dimethyl sulfate with N,N-dimethylformamide at temperate in the range of 60°C to 120°C to obtain the reaction mass, followed by addition of sodium methoxide at temperate in the range of 0°C to 60°C and fractional distillation of reaction mass using Vigreux column at temperate in the range of about 80°C to 110°C to isolate pure dimethylformamide dimethylacetal.

The process for the preparation of dimethylformamide dimethylacetal may be illustrated by following scheme-1.

Having described the invention with reference to certain preferred embodiments, other embodiments will become apparent to one skilled in the art from consideration of the specification.
The process for the preparation of dimethylformamide dimethylacetal and its intermediate described in the present invention is demonstrated in examples illustrated below. This example is provided as illustration only and therefore should not be construed as limitation of the scope of invention.
Example: Preparation of dimethylformamide dimethylacetal
126g (1.0 mole) of dimethylsulfate was added in round bottom flask. 73g (1.0 mole) of N,N-dimethylformamide was added and heated to 80°C for about 3-4 hours. The reaction mass is cooled and formed reaction mass. The 216gm (1.0 mole) sodium methoxide solution (25%w/v) was chilled to 0-5°C and added to the reaction mass. The temperature of the reaction mass was raised to about 20-30°C stirred for about one hour ad further raised to about

60-70°C. The reaction mass is distilled to obtain the mixture of methanol and dimethylformamide dimethylacetal.
The isolated mixture of methanol and dimethylformamide dimethylacetal was fractionally distilled using Vigreux® column and isolated methanol first at about temperature 64-80°C and then dimethylformamide dimethylacetal was isolated at about 80-110°C. Yield 70 - 75 gm. Purity by G.C (93 - 95 %).

We claim:
1. An improved process for the preparation of dimethylformamide dimethylacetal of formula (I)

which comprise;
(a) reacting dimethyl sulfate of formula (II) with N,N-dimethylformamide in the presence of a solvent or absent of a solvent at a temperature in the range of 60°C to 120°C to obtain reaction mass;

(b) reacting the reaction mass with sodium methoxide; and
(c) isolating dimethylformamide dimethylacetal of formula (I)

3. The process as claimed claim 1, wherein the solvent is alcohol selected from methanol, ethanol, isopropanol, n-propanol, water or mixture therefore.
4. The process as claimed in claim 1, wherein the reaction is carried out in absent of solvent.
5. The process as claimed in claim 1, where in dimethylformamide dimethylacetal is isolated by fractional distillation using Vigreux column.

6. The process as claimed in claim 5, wherein dimethylformamide dimethylacetal is isolated at temperate in the range of about 80°C to 110°C.
7. A process for the preparation of Dimethylformamide dimethylacetal, which comprises reaction of dimethyl sulfate with N,N-dimethylformamide at temperate in the range of 60°C to 120°C to obtain the reaction mass, followed by addition of sodium methoxide at temperate in the range of 0°C to 60°C and fractional distillation of reaction mass using Vigreux column at temperate in the range of about 80°C to 110°C to isolate pure dimethylformamide dimethylacetamide.
8. The process as claimed in claim 7, wherein the purity of dimethylformamide dimethylacetal is more than 93% as determined by Gas chromatography.
9. A process for preparing Dimethylformamide dimethylacetal of formula (I) such as herein described in accordance with accompanying text, description and examples thereof.