FORM-2
THE PATENT ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(see section 10 and rule 13)
SYNTHESIS OF SUBSTITUTED PYRIMIDINE DERIVATIVES
GHARDA CHEMICALS LTD.
an Indian Company
of B-27/29, MIDC Dombivli (East)
Thane-421203, India
Inventors:
1. MATHUR SUCHET S.
2. VIJAYANANITH
3. NOUGARE VINA YAK H.
4. BHOSALE SACHIN R.
5. DAPAKEMANGESHK.
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

FIELD OF THE DISCLOSURE
The present disclosure relates to a process for the preparation of substituted pyrimidine derivatives. More particularly, the present disclosure relates to a process for the preparation of 4,6-dialkoxy-2-(alkylsulfonyl)pyrimidine.
BACKGROUND
4,6-dialkoxy-2-(alkylsulfonyl)pyrimidine is one of the derivatives of 2-alkylsulfonylpyrimidine which can be used as an intermediate for the synthesis herbicides such as Bispyribac-sodium.

4, 6-dialkoxy-2-(alkylsulfonyl) pyrimidine
Synthesis of 4,6-dialkoxy-2-(alkylsulfonyl)pyrimidine has been disclosed in some of the prior art documents. For instance, WO2000046212 discloses preparation of 4.6-dimethoxy-2-fmethylsulphonyl) pyrimidine. The process involves mixing 2-methylthiobarbituric acid in xylene, triphenylphosphine oxide and tetrabutylammonium chloride followed by heating and passing phosgene until reaction of the adduct is complete. In the subsequent stage, phosgene is removed from the reaction mass followed by extracting the organic phase with water and reacting with sodium methylate at 50°C to form 4,6-dimethoxy-2-methylthiopyrimidine. Further, 5 mol% of sodium tungstate and 5 mol% of tetrabutylammonium chloride are added to. the reaction mixture and mixed at 85°C with 2 molar equivalents of hydrogen peroxide.
WO2002008207 discloses a process for preparing 4, 6-dimethoxy- 2-(methylsulfonyl) -1, 3-pyrimidine by reacting 4,6- dichloro-2- (methylthio) -1, 3-pyrimidine in an inert organic solvent with an alkali metal methoxide, transfer of the

resulting 4, 6-dimethoxy-2- (methylthio) - 1, 3-pyrimidine into an aqueous-acidic medium and subsequent oxidation of this compound, in the presence of tricaprylmethylammonium chloride as a catalyst, wherein the oxidation is followed by a purification step in which the aqueous- acidic reaction mixture is adjusted with aqueous base to a pH in the range of 5-8 and stirred either in the presence or in the absence of an organic solvent.
CN 101747283 discloses a method for the preparation of 4,6-dimethoxy-2-(methanesulfonyl)pyrimidine which involves chlorination of 4,6-dihydroxy-2-(methylthio)pyrimidine to obtain 4,6-dichloro-2-(methylthio)pyrimidine which on methoxylation gives 4,6-dimethoxy-2-(methylthio)pyrimidine followed by oxidation. The process disclosed in CN 101747283 particularly employs trifluoromethane sulfonic acid salt, quaternary ammonium salt or organic bases catalyst in methoxylation reaction. The catalyst is selected from the group consisting of copper trifluoromethane sulfonate, trifluoromethane sulfonate, tin trifluoromethyl sulfonate, trioctyl methyl chloride ammonium, tertiary ammonium chloride and triethylamine.
The processes disclosed in the prior art are associated with the disadvantages such as low product yield, low purity, and use of expensive chemicals. Therefore, there is a need to provide an improved process for the preparation of 4,6-disubstituted 2-alkylsulfonylpyrimidine derivatives that is cost efficient and provides product with high purity and with improved yield and uses cost-effective industrial chemicals.
OBJECTS
Some of the objects of the present disclosure are described herein below:
It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
Another object of the present disclosure is to provide a process for the preparation of 4,6-dialkoxy 2-(alkylsulfonyl)pyrimidine.

Still another object of the present disclosure is to provide a simple and cost efficient process for the preparation of 4,6-dialkoxy 2-(alkylsulfonyl)pyrimidine.
Yet another object of the present disclosure is to provide a high yielding process for the preparation of 4,6-dialkoxy 2-(alkylsulfonyl)pyrimidine.
A further object of the present disclosure is to provide a process for the preparation of 4,6-dialkoxy 2-(alkylsulfonyl)pyrimidine of high purity.
Other objects and advantages of the present disclosure will be more apparent from the following description when read in conjunction with the accompanying figures, which are not intended to limit the scope of the present disclosure.
Summary
The present disclosure provides a process for the preparation of 4,6-dialkoxy-2-(alkylsulfonyl)pyrimidine, said process comprising the following steps: i. reacting dialkyl malonate and thiourea in the presence of sodium alkoxide and an alcohol to obtain a sodium salt of thiobarbituric acid;
ii. alkylating said salt of thiobarbituric acid with alkyl chloride to obtain 2-alkyl thio-4,6-dihydroxypyrimidine;
iii. chlorinating said 2-alkyIthio-4,6-dihydroxypyrimidine with phosphoryl chloride (P0C13) to obtain 2-alkylthio-4,6-dichloropyrimidine;
iv. alkoxylating said 2-alkyl thio-4,6-dichloropyrimidine with sodium alkoxide to obtain 4,6-dialkoxy-2-(alkyIthio) pyrimidine; and
v. oxidizing said 4,6-dialkoxy-2-(alkylthio) pyrimidine in the presence of hydrogen peroxide, acetic acid and a catalyst and to obtain 4,6-dialkoxy-2-(alkylsulfonyl) pyrimidine.

Typically, dialkyl malonate is selected from the group consisting of dimethyl malonate, diethyl malonate, di-n-propyl malonate and di-n-butyl malonate, preferably, dimethyl malonate.
Typically, sodium alkoxide is sodium methoxide.
Typically, 2-aIkyI thio-4,6-dihydroxypyrimidine is 2-methyI thio-4,6-
dihydroxypyrimidine.
Typically, 2-alkyl thio-4,6-dichloropyrimidine is 2-methyl thio-4,6-
dichloropyrimidine.
Typically, 4,6-dialkoxy-2-(alkylthio) pyrimidine is 4,6-dimethoxy-2-(methylthio)
pyrimidine.
Typically, 4,6-dialkoxy-2-(alkylsulfonyl) pyrimidine is 4,6-dimethoxy-2-(methylsulfonyl) pyrimidine.
Typically, the alcohol is selected from the group consisting of methanol, ethanol, n-propyl alcohol and n-butyl alcohol.
Typically, alkyl chloride is methyl chloride.
Typically, the step (i) comprises adding dimethyl malonate and thiourea to methanol to obtain a mass, heating the mass to a temperature ranging between 50 and 70°C, incorporating a methanolic solution of sodium methoxide to said mass obtain a mixture, maintaining said mixture at a temperature ranging between 50 and 70°C for a period of 1 to 5 hours, removing methanol from said mixture by distillation to obtain a second mass, cooling said mass to obtain a cooled mass, filtering said mass to obtain a cake; and washing said cake with methanol followed by drying to obtain a sodium salt of thiobarbituric acid.

Typically, the step (ii) comprises mixing sodium salt of thiobarbituric acid with sodium hydroxide solution and methanol to obtain a mass, adding methyl chloride to said mass and stirring to obtain 2-methylthio-4,6-dihydroxypyrimidine.
Typically, the step (iii) comprises mixing 2-methylthio-4,6-dihydroxypyrimidine, POCl3 at least one aromatic hydrocarbon and at least one base to obtain a mixture, heating said mixture to a temperature ranging between 40 to 90 C to obtain a heated mixture, and adding POCl3 and chlorine into said heated mixture followed by stirring at temperature of 40 to 60°C to obtain 2-methylthio-4,6-dichloropyrimidine.
Typically, the step (iv) comprises mixing an alcoholic solution of sodium methoxide, cuprous chloride and sodium iodide to obtain a mixture, cooling said mixture followed by adding 2-methylthio-4,6-dichloropyrimidine to at a temperature ranging between 15 and 25°C to obtain a mass and heating said mass at a temperature ranging between 30 and 50 °C to obtain 4,6-dimethoxy-2-(methylthio) pyrimidine.
Typically, the step (v) comprises mixing 4,6-dimethoxy-2-(methylthio) pyrimidine, sodium tunstate and acetic acid to obtain a mixture, heating said mixture and adding hydrogen peroxide (H2O2) to obtain 4,6-dimethoxy-2-(metbylsulfonyl) pyrimidine.
Typically, the catalyst is sodium tungstate.
Typically, the aromatic hydrocarbon is selected from the group consisting of
monochlorobenzene, and o-dichlorobenzene.
Typically, the base is selected from the group consisting of triethylamine,
tripropylamine and tributylamine.
Brief description of accompanying drawing:
Figure I illustrates the reaction scheme of the present disclosure.

Detailed description:
The present disclosure provides a process for the preparation of 4,6-dialkoxy-2-(alkylsulfonyl)pyrimidine.
In the first step, dialkyl malonate is reacted with thiourea in the presence of sodium alkoxide and an alcohol to obtain a sodium salt of thiobarbituric acid. The dialkyl malonate is selected from the group consisting of dimethyl malonate, diethyl malonate, di-n-propyl malonate and di-n-butyl malonate, preferably, dimethyl malonate. The alcohol is selected from the group consisting of methanol, ethanol, n-propyl alcohol and n-butyl alcohol.
The obtained salt of thiobarbituric acid is alkylated with alkyl chloride to obtain 2-
alkyl thio-4,6-dihydroxypyrimidine.
In the next step, 2-alkylthio-4,6-dihydroxypyrimidine is subjected to chlorination
using phosphoryl chloride (POCl3)to obtain 2-alkylthio-4,6-dichloropyrimidine which
is then alkoxylated with sodium alkoxide to obtain 4,6-dialkoxy-2-(alkylthio)
pyrimidine.
Finally, the obtained 4,6-dialkoxy-2-(alkylthio) pyrimidine is oxidized in the presence
of hydrogen peroxide, acetic acid and a catalyst and to obtain 4,6-dialkoxy-2-
(alkylsulfonyl) pyrimidine. The catalyst employed in oxidation step is sodium
tungstate.
The present disclosure particularly provides preparation of 4,6-dimethoxy-2-
(methylsulfonyl)pyrimidine.
In the first step, dimethyl malonate is reacted with thiourea in the presence of sodium
methoxide and methanol to obtain a sodium salt of thiobarbituric acid. The obtained
salt of thiobarbituric acid is alkylated with methyl chloride to obtain 2-methyI thio-
4,6-dihydroxypyrimidine.
In the next step, 2-methylthio-4,6-dihydroxypyrimidine is subjected to chlorination
using phosphoryl chloride (POCl3) to obtain 2-methyIthio-4,6-dichloropyrimidine
which is then alkoxylated with sodium methoxide to obtain 4,6-dimethoxy-2-
(methylthio) pyrimidine.

Finally, the obtained 4,6-dimethoxy-2-(methylthio) pyrimidine is oxidized in the presence of hydrogen peroxide, acetic acid and a catalyst and to obtain 4,6-dimethoxy-2-(methylsulfonyl) pyrimidine.
In one exemplary embodiment the preparation of a sodium salt of thiobarbituric acid involves the following steps:
- adding dimethyl malonate and thiourea to methanol to obtain a mass, heating the mass to a temperature ranging between 50 and 70 C,
- incorporating a methanolic solution of sodium methoxide to said mass over a period of 2 hours to obtain a mixture, maintaining said mixture at a temperature ranging between 50 and 70°C for a period of 1 to 5 hours,
- removing methanol from said mixture by distillation to obtain a second mass, cooling said mass to obtain a cooled mass, filtering said mass to obtain a cake; and
- washing said cake with methanol followed by drying to obtain a sodium salt of thiobarbituric acid.
In one exemplary embodiment the preparation of 2-methylthio-4,6-dihydroxypyrimidine involves the following steps:
- mixing sodium salt of thiobarbituric acid with sodium hydroxide solution and methanol to obtain a mass,
- adding methyl chloride to said mass, and stirring said mass to obtain 2-methylthio-4,6-dihydroxypyrimidine.
In one exemplary embodiment the preparation of 2-methylthio-4,6-dichloropyrimidine involves the following steps:
- mixing 2-methylthio-4,6-dihydroxypyrimidine, POCl3, at least one aromatic hydrocarbon and at least one base to obtain a mixture,
- heating said mixture to a temperature ranging between 40 to 90°C to obtain a heated mixture, and
- adding POCl3 and chlorine into the heated mixture followed by stirring at a temperature of 40 to 60°C to obtain 2-methylthio-4,6-dichloropyrimidine.

The aromatic hydrocarbon is selected from the group consisting of monochlorobenzene and o-dichlorobenzene and the base is selected from the group consisting of triethylamine, tripropylamine and tributylamine.
In one exemplary embodiment the preparation of 4,6-dimethoxy-2-(methylthio) pyrimidine involves the following steps:
- mixing an alcoholic solution of sodium methoxide, cuprous chloride and sodium iodide to obtain a mixture,
- cooling the mixture followed by adding 2-methylthio-4,6-dichIoropyrimidine at a temperature ranging between 15 and 25°C to obtain a mass, and
- heating said mass at a temperature ranging between 30 and 50 °C to obtain
- 4,6-dimethoxy-2-(methylthio) pyrimidine.
In one exemplary embodiment the preparation of 4,6-dimethoxy-2-(methylsulfonyl) pyrimidine involves the following steps:
- mixing 4,6-dimethoxy-2-(methylthio) pyrimidine, sodium tungstate and acetic acid to obtain a mixture, and
- adding hydrogen peroxide (H2O2) to the mixture to obtain 4,6-dimethoxy-2-(methylsulfonyl) pyrimidine.
The disclosure is further illustrated by way of the following non limiting examples. Example 1: Preparation of Thiobarbituric acid sodium salt A solution of 1,10m thiourea and 1.0m dimethylmalonate in 280ml methanol was refluxed and a solution of 1.0m sodium methoxide in 150ml methanol was added over 15 to 45 minutes. Mass was refluxed for 4 hours and part of methanol was distilled. The resulting mass was cooled below 30°C, filtered and washed with methanol. The obtained cake was dried to obtain thiobarbituric acid sodium salt (yield: 90%). Filtrate was concentrated to a level of 250- 280 ml. To this, 0.1m dimethyl malonate and 0.1m sodium methoxide solution were added. The obtained reaction mass was worked up as above. The yield of thiobarbituric acid sodium salt was 2%.

Example 2:
Preparation of 2-MethyIthio-4,6-dihydroxypyrimidine
1.0m thiobarbituric acid sodium salt was dissolved in 1.5m 1 N aqueous sodium hydroxide solution and 50 ml methanol in a SS autoclave to obtain a mixture. To this 0.5m methyl chloride was fed in 1 to 2 hours. The obtained reaction mass was stirred for 2 to 6 hours at 25-30°C, a second lot of 0.5m methyl chloride was fed in 1 to 2 hours and mass was stirred at 25-30°C for 6-8 hours. To this, 0.05m methyl chloride was fed and reaction mass was stirred for 2 to 6 hours. After the end of reaction HPLC indicated 85% 2-methylthio- 4, 6-dihydroxypyrimidine and 5% 2-methylthio-4-methoxy-6-hydroxypyrimidine. Yield of product was 75-80 mole %.
Example 3:
Preparation of 2-methyIthio-4, 6-dichIoropyrimidine
To 4m monochlorobenzene, 1.0 m 2-methyIthio-4,6-dihydoxypyrimidine was added. To this, 2.2m POCl3 was added in 1 to 2 hours and 2.2 m triethylamine was added over 2 to 4 hours at 40-50°C.The obtained mixture was heated to 80°C which resulted in a clear solution and stirred for 4-8 hours to obtain a mass. The obtained mass was cooled to 60°C. To this 2.0m phosphorus trichloride was added. Then 2.0m chlorine was fed in 6-10 hours at 60°C and stirred at 60°C for 8 to 10 hours. CI2 feeding was carried out in absence of light to avoid side chain chlorination. POCl3 was vacuum distilled and 200ml monochlorobenzene was added and continued the distillation to ensure complete removal of POCl3. 4.0m to 4.3m POCl3 was recovered; the residual mass was drowned in 200ml ice water and extracted with monochlorobenzene. To the monochlorobenzene layer, 100 ml water was added and neutralized with NaHC03. The layers were separated and monochlorobenzene layer was concentrated under vacuum. Yield of product was 85-87%,
Product was vacuum distilled and then crystallized using methanol to get 85 mole % with 99% purity.

Example 4:
Preparation of 4,6-dimethoxy-2-(methylthio)pyrimidine
To 2.2 m 3 N sodium methoxide solution in methanol was added 2m% cuprous chloride and 2m% sodium iodide to obtain a mixture which was then cooled to 20°C. 1.0m 2-methyl thio-4,6-dichloropyrimidine was dissolved in 400ml methanol and was added to the mixture over 3-6 hours and stirred for 1 hour at 20°C to obtain a reaction mass. The temperature of mass was raised to 30°C and then to 40°C, and stirred at 40°c for 6-12 hours, HPLC indicate 95-96% 2-methylthio-4,6-dimethoxypyrimidine and 0.5% 2-methyIthio-4-methoxy-6-chloropyrimidine. The mass was cooled and sodium chloride was filtered off. From the filtrate, methanol was distilled, water was added to residual mass and extracted with toluene. Toluene layer was washed with water and then concentrated. Yield of product was 90%.
Example 5: Preparation of 4,6-dimethoxy-2-(methylsulfonyl) pyrimidine
To 200ml acetic acid was added 3m% sodium tungstate. To this, 1.0m 2-methylthio-4,6-dimethoxypyrimidine was added to obtain a mass (clear solution). The mass was heated to 40°C. To the heated mass 2.1m 30% H2O2 was added in 4-8 hours and stirred at 40°c for 3-5 hours. Further, 0.05m 30 % H2O2 was added and stirred at 40°C till complete conversion. Reaction was carried out at 40°c. Reaction mixture was cooled and solids were filtered. The obtained cake was washed with aqueous acetic acid followed by water. The cake was then dried. Yield = 83%. The filtrate was extracted with ethylene dichloride. The obtained ethylene dichloride layer was concentrated, wt = 42g, yield of product was about 1-1.5%.
TECHNICAL ADVANTAGES:
The present disclosure related to a process for the preparation of 4,6-dialkoxy-2-(alkylsulfonyl)pyrimidine has the following technical advantages:
(1) low reaction temperature;
(2) minimal use of catalyst;
(3) less distillation problems;
(4) cost efficient; and

(5) use of readily available industrial chemicals.
"Whenever a range of values is specified, a value up to 10 % below and above the lowest and highest numerical value respectively, of the specified range, is included in the scope of the disclosure".
While considerable emphasis has been placed herein on the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiments as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the forgoing descriptive matter to be implemented merely as illustrative of the disclosure and not as limitation.
Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the invention as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or

quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.

WE CLAIM:
1. A process for the preparation of 4,6-dialkoxy-2-(alkylsulfonyl)pyrimidine, said
process comprising the following steps: i. reacting dialkyl malonate and thiourea in the presence of sodium alkoxide and an alcohol to obtain a sodium salt of thiobarbituric acid;
ii. alkylating said salt of thiobarbituric acid with alkyl chloride to obtain 2-alkyl thio-4,6-dihydroxypyrimidine;
iii. chlorinating said 2-alkylthio-4,6-dihydroxypyrimidine with phosphoryl chloride (POCyto obtain 2-alkylthio-4,6-dichloropyrimidine;
iv. alkoxylating said 2-alkyl thio-4,6-dichloropyrimidine with sodium alkoxide to obtain 4,6-dialkoxy-2-(alkylthio) pyrimidine; and
v. oxidizing said 4,6-dialkoxy-2-(alkylthio) pyrimidine in the presence of hydrogen peroxide, acetic acid and a catalyst and to obtain 4,6-dialkoxy-2-(alkylsulfonyl) pyrimidine.
2. The process as claimed in claim 1, wherein dialkyl malonate is selected from the group consisting of dimethyl malonate, diethyl malonate, di-n-propyl malonate and di-n-butyl malonate, preferably, dimethyl malonate.
3. The process as claimed in claim 1, wherein sodium alkoxide is sodium methoxide.
4. The process as claimed in claim 1, wherein alkyl chloride is methyl chloride.
5. The process as claimed in claim 1, wherein 2-alkyl thio-4,6-dihydroxypyrimidine is 2-methyl thio-4,6-dihydroxypyrimidine.
6. The process as claimed in claim 1, wherein 2-alkyl thio-4,6-dichloropyrimidine is 2-methyl thio-4,6-dichloropyrimidine.

7. The process as claimed in claim 1, wherein 4,6-dialkoxy-2-(alkyIthio) pyrimidine is 4,6-dimethoxy-2-(methylthio) pyrimidine.
8. The process as claimed in claim 1, wherein 4,6-dialkoxy-2-(alkylsulfonyl) pyrimidine is 4,6-dimethoxy-2-(methylsulfonyl) pyrimidine.
9. The process as claimed in claim 1, wherein the alcohol is selected from the group consisting of methanol, ethanol, n-propyl alcohol and n-butyl alcohol.
10. The process as claimed in claim 1, wherein the step (i) comprises adding dimethyl malonate and thiourea to methanol to obtain a mass, heating the mass to a temperature ranging between 50 and 70°C, incorporating a methanolic solution of sodium methoxide to said mass to obtain a mixture, maintaining said mixture at a temperature ranging between 50 and 70 C for a period of 1 to 5 hours, removing methanol from said mixture by distillation to obtain a second mass, cooling said mass to obtain a cooled mass, filtering said mass to obtain a cake; and washing said cake with methanol followed by drying to obtain a sodium salt of thiobarbituric acid.
11. The process as claimed in claim 1, wherein the step (ii) comprises mixing sodium salt of thiobarbituric acid with sodium hydroxide solution and methanol obtain a mass, adding methyl chloride to said mass and stirring to obtain 2-methylthio-4,6-dihydroxypyrimidine.
12. The process as claimed in claim 1, wherein the step (iii) comprises mixing 2-methylthio-4,6-dihydroxypyrimidine, POCI3, at least one aromatic hydrocarbon and at least one base to obtain a mixture, heating said mixture to a temperature ranging between 40 to 90°C to obtain a heated mixture, and adding POCI3 and chlorine into said heated mixture followed by stirring at a temperature of 40 to 60° to obtain 2-methyIthio-4,6-dichloropyrimidine.
13.The process as claimed in claim 1, wherein the step (iv) comprises mixing an alcoholic solution of sodium methoxide, cuprous chloride and sodium iodide to obtain a mixture, cooling said mixture followed by adding 2- methylthio-4,6-dichloropyrimidine at a temperature ranging between 15 and 25°C to obtain a mass, and heating said mass at a temperature ranging between 30 and 50 C to obtain 4,6-dimethoxy-2-(methylthio) pyrimidine.

14. The process as claimed in claim 1, wherein the step (v) comprises mixing 4,6-
dimethoxy-2-(methylthio) pyrimidine, sodium tungstate and acetic acid to
obtain a mixture, heating said mixture and adding hydrogen peroxide (H2O2) to
obtain 4,6-dimethoxy-2-(methylsulfonyl) pyrimidine.
15. The process as claimed in claim 1, wherein the catalyst is sodium tungstate.
16.The process as claimed in claim 12, wherein the aromatic hydrocarbon is
selected from the group consisting of monochlorobenzene and o-dichlorobenzene. 17. The process as claimed in claim 12, wherein the base is selected from the group consisting of triethylamine, tripropylamine and tributylamine.