Title of Invention	PROCESS FOR THE SYNTHESIS OF A HERBICIDALLY ACTIVE SALT OF PYRIMIDINYLOXYBENZOIC ACID
Abstract	A process for synthesis of a herbicidally active salt of pyrimidinyloxy benzoic acid having the formula in high yields, wherein M+ is an alkali metal ion or an ammonium ion. A hydroxy substituted benzoic acid is reacted with a pyrimidine in the presence of a phase transfer catalyst at a temperature in the range of 50 to 110 C in the presence of an inert organic solvent taken in a quantity of 4 to 5 liters per mole of any of the reactants and at a hydroxyl ion concentration required to maintain a pKa in the range of 7.5 to 9.0. The invention also relates to the herbicidally active salt prepared by the process, to the salt compositions and to a method of killing weeds by using the composition.

Title of Invention

PROCESS FOR THE SYNTHESIS OF A HERBICIDALLY ACTIVE SALT OF PYRIMIDINYLOXYBENZOIC ACID

Abstract

A process for synthesis of a herbicidally active salt of pyrimidinyloxy benzoic acid having the formula in high yields, wherein M+ is an alkali metal ion or an ammonium ion. A hydroxy substituted benzoic acid is reacted with a pyrimidine in the presence of a phase transfer catalyst at a temperature in the range of 50 to 110 C in the presence of an inert organic solvent taken in a quantity of 4 to 5 liters per mole of any of the reactants and at a hydroxyl ion concentration required to maintain a pKa in the range of 7.5 to 9.0. The invention also relates to the herbicidally active salt prepared by the process, to the salt compositions and to a method of killing weeds by using the composition.

Full Text	FORM 2 THE PATENTS ACT, 1970 (39 of 1970) As amended by the Patents (Amendment) Act, 2005 & The Patents Rules, 2003 As amended by the Patents (Amendment) Rules, 2006 COMPLETE SPECIFICATION (See section 10 and rule 13) TITLE OF THE INVENTION A process for synthesis of herbicidally active salt of pyrimidinyloxybenzoic acid APPLICANTS GODREJ AGROVET LTD, PIROJSHANAGAR, EASTERN EXPRESS, HIGHWAY, VIKHROLI - EAST, MUMBAI 400 079. MAHARASHTRA, INDIA, AN INDIAN COMPANY INVENTORS Iyer Ramaswamy, Waghmare Samson Lucas, Dr Vyas Brahmanand Ambashankar, Dr Mistry Keki Bamanshaw and Godrej Nadir Burjor, all of GODREJ AGROVET LTD, PIROJSHANAGAR, EASTERN EXPRESS HIGHWAY, VIKHROLI - EAST, MUMBAI 400 079. MAHARASHTRA, INDIA, ALL INDIAN NATIONALS PREAMBLE TO THE DESCRIPTION The following specification particularly describes the nature of this invention and the manner in which it is to be performed : FIELD OF THE INVENTION The invention relates to a process for synthesis of a herbicidally active salt of pyrimidinyloxy benzoic acid, in high yields, by reacting a hydroxy substituted benzoic acid with a pyrimidine at a pKa of 7.5 to 9.0. The invention also relates to the herbicidally active salt, compositions thereof and to a method for killing weeds using the composition. BACKGROUND OF THE INVENTION Pyrimidine derivatives of benzoic acid are widely used as herbicides. They are usually synthesized by reacting pyrimidines with hydroxy substituted benzoic acid in the presence of a phase transfer catalyst. US 4906285 discloses a method for synthesizing herbicidally active pyrimidyl derivatives by condensation of a dihydroxy benzoic acid ester with a pynmidyl compound. The yield obtained by the condensation reaction is, however, low. CN 1396157 discloses a process for synthesis of pyrimidyl derivative of benzoic acid by reacting hydroxy benzoic acid with pyrimidine at reflux temperatures using benzene, tetrahydrofuran or ethanol as the solvent. DETAILED DESCRIPTION OF THE INVENTION It has been found by us by extensive research and experimentation that the pKa value plays a significant role in the yield of the herbicidally active salt of the invention and that high yields can be achieved with judicious pKa control. 2 Accordingly, the invention provides a process for synthesis of a herbicidally active salt of pyrimidinyloxy benzoic acid, in high yields, by reacting a hydroxy substituted benzoic acid with a pyrimidine at a pKa of 7.5 to 9.0 In one embodiment the invention provides a process for synthesis of a herbicidally active salt of pyrimidinyloxy benzoic acid having the formula in high yields, wherein M is an alkali metal ion or an ammonium ion, the process comprising reacting a hydroxy substituted benzoic acid with a pyrimidine in the presence of a phase transfer catalyst, the reaction being carried out at a temperature in the range of 50 toll0°C in the presence of an inert organic solvent taken in a quantity of 4 to 5 liters per mole of any of the reactants and at a hydroxyl ion concentration required to maintain a pKa in the range of 7.5 to 9.0. In another embodiment, the invention provides a process for synthesis of a herbicidally active salt of pyrimidinyloxy benzoic acid having the formula 3 H3CO H3CO OCH OCH- in high yields, wherein M+ is as defined herein, the process comprising reacting a hydroxy substituted benzoic acid with a pyrimidine in the presence of a phase transfer catalyst the reaction being carried out at a temperature in the range of 50 to 110°C in the presence of an inert organic solvent taken in a quantity of 4 to 5 liters per mole of any of the reactants and at a hydroxyl ion concentration required to maintain a pKa in the range of 7.5 to 9.0 wherein the process is carried out in a single stage. In another embodiment, the invention provides a process for synthesis of a herbicidally active salt of pyrimidinyloxy benzoic acid having the formula H3CO H3CO OCH- OCH- 4 in high yields, wherein M+ is as defined herein, the process comprising reacting a hydroxy substituted benzoic acid with a pyrimidine in the presence of a phase transfer catalyst, the reaction being carried out at a temperature in the range of 50 toll0°C in the presence of an inert organic solvent taken in a quantity of 4 to 5 liters per mole of any of the reactants and at a hydroxyl ion concentration required to maintain a pKa in the range of 7.5 to 9.0 wherein the hydroxyl ion concentration is maintained by an alkali metal hydroxide In another embodiment, the invention provides a process for synthesis of a herbicidally active salt of pyrimidinyloxy benzoic acid having the formula in high yields, wherein M+ is as defined herein, the process comprising reacting a hydroxy substituted benzoic acid with a pyrimidine in the presence of a phase transfer catalyst, the reaction being carried out at a temperature in the range of 50 to 110°C in the presence of an inert organic solvent taken in a quantity of 4 to 5 liters per mole of any of 5 the reactants and at a hydroxyl ion concentration required to maintain a pKa in the range of 7.5 to 9.0 wherein the hydroxyl ion concentration is maintained by sodium hydroxide In another embodiment, the invention provides a process for synthesis of a herbicidally active salt of pyrimidinyloxy benzoic acid having the formula in high yields, wherein M+ is as defined herein, the process comprising reacting a hydroxy substituted benzoic acid with a pyrimidine in the presence of a phase transfer catalyst, the reaction being carried out at a temperature in the range of 50 to 110 C in the presence of an inert organic solvent taken in a quantity of 4 to 5 liters per mole of any of the reactants and at a hydroxyl ion concentration required to maintain a pKa in the range of 7.5 to 9.0 wherein the hydroxyl ion concentration is maintained by sodium hydroxide which is in the prill form In another embodiment, the invention provides a process for synthesis of a herbicidally active salt of pyrimidinyloxy benzoic acid having the formula 6 in high yields, wherein M+ is as defined herein, the process comprising reacting a hydroxy substituted benzoic acid with a pyrimidine in the presence of a phase transfer catalyst, the reaction being carried out at a temperature in the range of 50 to 110°C in the presence of an inert organic solvent taken in a quantity of 4 to 5 liters per mole of any of the reactants and at a hydroxyl ion concentration required to maintain a pKa in the range of 7.5 to 9.0 wherein the pyrimidine is 2-methyl suphonyl- 4, 6-dimethoxy pyrimidine. In another embodiment, the invention provides a process for synthesis of a herbicidally active salt of pyrimidinyloxy benzoic acid having the formula 7 H3CO H3CO OChi OCH- in high yields, wherein M+ is as defined herein, the process comprising reacting a hydroxy substituted benzoic acid with a pyrimidine in the presence of a phase transfer catalyst, the reaction being carried out at a temperature in the range of 50 to 110 C in the presence of an inert organic solvent taken in a quantity of 4 to 5 liters per mole of any of the reactants and at a hydroxyl ion concentration required to maintain a pKa in the range of 7.5 to 9.0 wherein the hydroxyl ion concentration is maintained by sodium hydroxide and the phase transfer catalyst is selected from quaternary ammonium salts, polyethylene glycols and crown ethers. In another embodiment, the invention provides a herbicidally active salt of pyrimidinyloxy benzoic acid having the formula H3CO H3CO in high yields, wherein M+ is as defined herein. In another embodiment, the invention provides a herbicidal composition comprising a herbicidally active salt of pyrimidinyloxy benzoic acid having the formula in high yields, wherein M is as defined herein. In a further embodiment, the invention provides a method of killing weeds, the method comprising spraying a herbicidal composition, the composition comprising a herbicidally active salt of pyrimidinyloxy benzoic acid having the formula 9 wherein M+ is as defined herein The invention provides a process for synthesis of salts of pyrimidinyloxy benzoic acid in high yields. The synthesized salt is herbicidally active and can be directly used in spray compositions for killing weeds. The process of invention involves condensation reaction between a hydroxy substituted benzoic acid and a pyrimidine. Advantageously, a diyhydoxy benzoic acid such as 2,6 dihydroxy benzoic acid is used for the condensation reaction. The condensation reaction is usually carried out in the presence of a phase transfer catalyst. The phase transfer catalyst is selected from quaternary ammonium salts, polyethylene glycols, crown ethers and related chemical moieties. Advantageously, tetra butylammonium bromide is used as the phase transfer catalyst. The process of the invention is carried out at a pKa in the range of 7.5 to 9.0. The pKa is controlled and maintained in this range by suitably selecting the quantity of the solvent, reactants and the base used for the reaction. An alkali metal such as sodium metal, potassium metal or an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide, an alkali metal carbonate such as sodium carbonate or potassium carbonate, an organic amine such as triethylamine or pyridine or an alkoxide such as sodium 10 methoxide or potassium t-butoxide can be used as the base for the reaction. Advantageously, an alkali metal hydroxide such as sodium hydroxide is used as the base. Usually, sodium hydroxide is used in the prill form. A hydrocarbon solvent such as benzene, toluene or xylene, a ketone solvent like acetone, methylethylketone, or an aprotic polar solvent like dimethylformamide or dimethyl sulfoxide, acetonitrile or water or a mixture thereof may be used or an alcohol solvent like methanol, ethanol or ether solvent like dioxane or tetrahydrofuran may be used or chlorinated solvent like methylene dichloride, ethylenedichloride may be used as the solvent for the reaction. Typically the organic solvent is taken in a quantity of 4-5 litres per mole of any of the reactants. The process of the invention is usually carried out in a single stage. The invention also provides a herbicidally active salt of pyrimidinyloxy benzoic acid. The salt can be an alkali metal salt such as a sodium salt or a potassium salt or an ammonium salt. The salt is usually obtained in high yields of above 72%. The salt is used to prepare herbicidal composition for killing weeds in an agricultural field. The compositions are usually prepared from the salt, in herbicidally effective amounts. The compositions can be formed into granules, powders, concentrates and can contain a carrier, adjuvant, a dispersing agent or a surfactant. The proportion of the salt in the composition can vary depending upon the application method, the application site etc. The composition is usually applied in the form of a spray. The invention is further illustrated by way of the following non limiting examples. 11 EXAMPLE 1 Preparation of sodium salt of 2,6-bis(4,6-dimethoxypyrimidin-2-yloxy) benzoic acid at a pKa in the range of 6.0 to 6.5 In a clean and dry flask, 1.54 g of 2,6-dihydroxy benzoic acid and 0.060 g of tetra butyl ammonium bromide as phase transfer catalyst was taken along with toluene solvent. 0.6 g of sodium hydroxide in fine prill form was added while stirring at reflux temperature for 1- 5 hrs to bring the pKa of the reaction mass to about 6.0 to 6.5 and then 2-methylsulfonyl-4,6-dimethoxy pyrimidine was added and the mixture further reacted with stirring for 12 to 18 hours to obtain the salt of 2,6-bis(4,6-dimethoxypyrimidin-2-yloxy ) benzoic acid. The reaction mass was filtered to recover the unreacted raw material and washed and dried to obtain the purified product. The salt was obtained in yield of 10%. EXAMPLE 2 Preparation of sodium salt of 2,6-bis(4,6-dimethoxypyrimidin-2-yloxy ) benzoic acid at a pKa in the range of 7.5 to 9.0 In a clean and dry flask 1.54 g of 2,6-dihydroxy benzoic acid and 0.060 g of tetra butyl ammonium bromide as phase transfer catalyst was taken along with toluene solvent. 1.2 g of sodium hydroxide in fine prill form was added while stirring and maintaining the temperature at 80°C for 1 to 5 hrs to bring the pKa of the reaction mass in the range of 7.5 to 9.0 and then 2-methylsulfonyl-4, 6-dimethoxy pyrimidine was added and the mixture further reacted with stirring for 12 to 18 hours to obtain the salt of 2,6-bis(4,6-dimethoxypyrimidin-2-yloxy) benzoic acid. The reaction mass was filtered to recover the 12 unreacted raw material and washed and dried to obtain the purified product. A high yield of the product was obtained ( 75 % ). The purified product was dissolved in water to get a known concentration which is suitable for spray application. EXAMPLE 3 Preparation of sodium salt of 2,6-bis(4,6-dimethoxypyrimidin-2-yloxy ) benzoic acid at a pKa in the range of 10.0 to 10.5 In a clean and dry flask 1.54 g of 2, 6-dihydroxy benzoic acid and 0.060 g of tetra butyl ammonium bromide as phase transfer catalyst was taken along with toluene solvent. 1.8 g of sodium hydroxide in fine prill form was added while stirring at reflux temperature for 1- 5 hrs to bring the pKa of the reaction mass to about 10.0 tol0.5 and then 2-methylsulfonyl-4, 6-dimethoxy pyrimidine was added and the mixture further reacted with stirring for 12 to 18 hours to get the salt of 2,6-bis (4,6-dimethoxypyrimidin-2-yloxy ) benzoic acid. The reaction mass was filtered to recover the unreacted raw material and washed and dried to obtain the purified product. As discussed in the foregoing, the process of the invention (as exemplified by Example 2 ), wherein the pKa in the range of 7.5 to 9.0 is maintained, results in pyrimidynyloxy benzoic acid salt in high yield of 75%. At pKa values higher than 9.0 (as employed in the experiment of example 3) or at a pKa value lower than 7.5 (as employed in the experiment of example 1), the yield of the salt is substantially lower. Higher yields would result in increased productivity, easier isolation and lesser purification procedures. 13 Further, in the process of the invention the reactants are recycled and reused. Thus, there is savings in the cost and the overall efficiency is improved. The above description is illustrative only and is not limiting- The invention is defined by the claims that follow and their full range of equivalents. 14 We claim: 1. A process for synthesis of a herbicidally active salt of pyrimidinyloxy benzoic acid having the formula in high yields, wherein M+ is an alkali metal ion or an ammonium ion, the process comprising reacting a hydroxy substituted benzoic acid with a pyrimidine in the presence of a phase transfer catalyst, the reaction being carried out at a temperature in the range of 50 to 110°C in the presence of an inert organic solvent taken in a quantity of 4 to 5 liters per mole of any of the reactants and at a hydroxyl ion concentration required to maintain a pKa in the range of 7.5 to 9.0. 2. The process as claimed in claim 1 wherein the process is carried out in a single stage. 15 16 3. The process as claimed in any one of the claims 1 or 2 wherein the hydroxyl ion concentration is maintained by an alkali metal hydroxide. 4. The process as claimed in claim 3 wherein the metal hydroxide is sodium hydroxide. 5. The process as claimed in claim 4 wherein the sodium hydroxide is in the prill form. 6. The process as claimed in anyone of the claims 1 to 5 wherein the pyrimidine is 2-methyl suphonyl- 4, 6-dimethoxy pyrimidine. 7. The process as claimed in any one of the claims 1 to 6, wherein the phase transfer catalyst is selected from quaternary ammonium salts, polyethylene glycols and crown ethers. 8. A herbicidally active salt of pyrimidinyloxy benzoic acid having the formula, wherein M is an alkali metal ion or an ammonium ion, the salt being synthesized by the process as claimed in any one of the claims 1 to 7. 9. A herbicidal composition comprising the salt as claimed in claim 8. 10. A method of killing weeds, the method comprising spraying the composition as claimed in claim 9. Dated this 14th day of August 2008 (Jose M A) ofKhaitan&Co Agent for the Applicants 17

Full Text

FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
A process for synthesis of herbicidally active salt of pyrimidinyloxybenzoic acid
APPLICANTS
GODREJ AGROVET LTD, PIROJSHANAGAR, EASTERN EXPRESS, HIGHWAY, VIKHROLI - EAST, MUMBAI 400 079. MAHARASHTRA, INDIA, AN INDIAN COMPANY
INVENTORS

Iyer Ramaswamy, Waghmare Samson Lucas, Dr Vyas Brahmanand
Ambashankar, Dr Mistry Keki Bamanshaw and Godrej Nadir Burjor, all of
GODREJ AGROVET LTD, PIROJSHANAGAR, EASTERN EXPRESS
HIGHWAY, VIKHROLI - EAST, MUMBAI 400 079. MAHARASHTRA, INDIA, ALL INDIAN NATIONALS
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed :

FIELD OF THE INVENTION
The invention relates to a process for synthesis of a herbicidally active salt of
pyrimidinyloxy benzoic acid, in high yields, by reacting a hydroxy substituted benzoic
acid with a pyrimidine at a pKa of 7.5 to 9.0. The invention also relates to the
herbicidally active salt, compositions thereof and to a method for killing weeds using the
composition.
BACKGROUND OF THE INVENTION
Pyrimidine derivatives of benzoic acid are widely used as herbicides. They are usually synthesized by reacting pyrimidines with hydroxy substituted benzoic acid in the presence of a phase transfer catalyst. US 4906285 discloses a method for synthesizing herbicidally active pyrimidyl derivatives by condensation of a dihydroxy benzoic acid ester with a pynmidyl compound. The yield obtained by the condensation reaction is, however, low. CN 1396157 discloses a process for synthesis of pyrimidyl derivative of benzoic acid by reacting hydroxy benzoic acid with pyrimidine at reflux temperatures using benzene, tetrahydrofuran or ethanol as the solvent.
DETAILED DESCRIPTION OF THE INVENTION
It has been found by us by extensive research and experimentation that the pKa value plays a significant role in the yield of the herbicidally active salt of the invention and that high yields can be achieved with judicious pKa control.
2

Accordingly, the invention provides a process for synthesis of a herbicidally active salt of pyrimidinyloxy benzoic acid, in high yields, by reacting a hydroxy substituted benzoic acid with a pyrimidine at a pKa of 7.5 to 9.0
In one embodiment the invention provides a process for synthesis of a herbicidally active salt of pyrimidinyloxy benzoic acid having the formula

in high yields, wherein M is an alkali metal ion or an ammonium ion, the process comprising reacting a hydroxy substituted benzoic acid with a pyrimidine in the presence of a phase transfer catalyst, the reaction being carried out at a temperature in the range of 50 toll0°C in the presence of an inert organic solvent taken in a quantity of 4 to 5 liters per mole of any of the reactants and at a hydroxyl ion concentration required to maintain a pKa in the range of 7.5 to 9.0.
In another embodiment, the invention provides a process for synthesis of a herbicidally active salt of pyrimidinyloxy benzoic acid having the formula
3

H3CO
H3CO

OCH OCH-

in high yields, wherein M+ is as defined herein, the process comprising reacting a hydroxy substituted benzoic acid with a pyrimidine in the presence of a phase transfer catalyst the reaction being carried out at a temperature in the range of 50 to 110°C in the presence of an inert organic solvent taken in a quantity of 4 to 5 liters per mole of any of the reactants and at a hydroxyl ion concentration required to maintain a pKa in the range of 7.5 to 9.0 wherein the process is carried out in a single stage.
In another embodiment, the invention provides a process for synthesis of a herbicidally active salt of pyrimidinyloxy benzoic acid having the formula

H3CO
H3CO

OCH-
OCH-

4

in high yields, wherein M+ is as defined herein, the process comprising reacting a hydroxy substituted benzoic acid with a pyrimidine in the presence of a phase transfer catalyst, the reaction being carried out at a temperature in the range of 50 toll0°C in the presence of an inert organic solvent taken in a quantity of 4 to 5 liters per mole of any of the reactants and at a hydroxyl ion concentration required to maintain a pKa in the range of 7.5 to 9.0 wherein the hydroxyl ion concentration is maintained by an alkali metal hydroxide
In another embodiment, the invention provides a process for synthesis of a herbicidally active salt of pyrimidinyloxy benzoic acid having the formula

in high yields, wherein M+ is as defined herein, the process comprising reacting a hydroxy substituted benzoic acid with a pyrimidine in the presence of a phase transfer catalyst, the reaction being carried out at a temperature in the range of 50 to 110°C in the presence of an inert organic solvent taken in a quantity of 4 to 5 liters per mole of any of
5

the reactants and at a hydroxyl ion concentration required to maintain a pKa in the range of 7.5 to 9.0 wherein the hydroxyl ion concentration is maintained by sodium hydroxide
In another embodiment, the invention provides a process for synthesis of a herbicidally active salt of pyrimidinyloxy benzoic acid having the formula

in high yields, wherein M+ is as defined herein, the process comprising reacting a hydroxy substituted benzoic acid with a pyrimidine in the presence of a phase transfer catalyst, the reaction being carried out at a temperature in the range of 50 to 110 C in the presence of an inert organic solvent taken in a quantity of 4 to 5 liters per mole of any of the reactants and at a hydroxyl ion concentration required to maintain a pKa in the range of 7.5 to 9.0 wherein the hydroxyl ion concentration is maintained by sodium hydroxide which is in the prill form
In another embodiment, the invention provides a process for synthesis of a herbicidally active salt of pyrimidinyloxy benzoic acid having the formula
6

in high yields, wherein M+ is as defined herein, the process comprising reacting a hydroxy substituted benzoic acid with a pyrimidine in the presence of a phase transfer catalyst, the reaction being carried out at a temperature in the range of 50 to 110°C in the presence of an inert organic solvent taken in a quantity of 4 to 5 liters per mole of any of the reactants and at a hydroxyl ion concentration required to maintain a pKa in the range of 7.5 to 9.0 wherein the pyrimidine is 2-methyl suphonyl- 4, 6-dimethoxy pyrimidine.
In another embodiment, the invention provides a process for synthesis of a herbicidally active salt of pyrimidinyloxy benzoic acid having the formula
7

H3CO
H3CO

OChi
OCH-

in high yields, wherein M+ is as defined herein, the process comprising reacting a hydroxy substituted benzoic acid with a pyrimidine in the presence of a phase transfer catalyst, the reaction being carried out at a temperature in the range of 50 to 110 C in the presence of an inert organic solvent taken in a quantity of 4 to 5 liters per mole of any of the reactants and at a hydroxyl ion concentration required to maintain a pKa in the range of 7.5 to 9.0 wherein the hydroxyl ion concentration is maintained by sodium hydroxide and the phase transfer catalyst is selected from quaternary ammonium salts, polyethylene glycols and crown ethers.
In another embodiment, the invention provides a herbicidally active salt of pyrimidinyloxy benzoic acid having the formula

H3CO
H3CO

in high yields, wherein M+ is as defined herein.
In another embodiment, the invention provides a herbicidal composition comprising a herbicidally active salt of pyrimidinyloxy benzoic acid having the formula

in high yields, wherein M is as defined herein.
In a further embodiment, the invention provides a method of killing weeds, the method comprising spraying a herbicidal composition, the composition comprising a herbicidally active salt of pyrimidinyloxy benzoic acid having the formula
9

wherein M+ is as defined herein
The invention provides a process for synthesis of salts of pyrimidinyloxy benzoic acid in high yields. The synthesized salt is herbicidally active and can be directly used in spray compositions for killing weeds. The process of invention involves condensation reaction between a hydroxy substituted benzoic acid and a pyrimidine. Advantageously, a diyhydoxy benzoic acid such as 2,6 dihydroxy benzoic acid is used for the condensation reaction. The condensation reaction is usually carried out in the presence of a phase transfer catalyst. The phase transfer catalyst is selected from quaternary ammonium salts, polyethylene glycols, crown ethers and related chemical moieties. Advantageously, tetra butylammonium bromide is used as the phase transfer catalyst.
The process of the invention is carried out at a pKa in the range of 7.5 to 9.0. The pKa is controlled and maintained in this range by suitably selecting the quantity of the solvent, reactants and the base used for the reaction. An alkali metal such as sodium metal, potassium metal or an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide, an alkali metal carbonate such as sodium carbonate or potassium carbonate, an organic amine such as triethylamine or pyridine or an alkoxide such as sodium
10

methoxide or potassium t-butoxide can be used as the base for the reaction. Advantageously, an alkali metal hydroxide such as sodium hydroxide is used as the base. Usually, sodium hydroxide is used in the prill form. A hydrocarbon solvent such as benzene, toluene or xylene, a ketone solvent like acetone, methylethylketone, or an aprotic polar solvent like dimethylformamide or dimethyl sulfoxide, acetonitrile or water or a mixture thereof may be used or an alcohol solvent like methanol, ethanol or ether solvent like dioxane or tetrahydrofuran may be used or chlorinated solvent like methylene dichloride, ethylenedichloride may be used as the solvent for the reaction. Typically the organic solvent is taken in a quantity of 4-5 litres per mole of any of the reactants. The process of the invention is usually carried out in a single stage.
The invention also provides a herbicidally active salt of pyrimidinyloxy benzoic acid. The salt can be an alkali metal salt such as a sodium salt or a potassium salt or an ammonium salt. The salt is usually obtained in high yields of above 72%. The salt is used to prepare herbicidal composition for killing weeds in an agricultural field. The compositions are usually prepared from the salt, in herbicidally effective amounts. The compositions can be formed into granules, powders, concentrates and can contain a carrier, adjuvant, a dispersing agent or a surfactant. The proportion of the salt in the composition can vary depending upon the application method, the application site etc. The composition is usually applied in the form of a spray.
The invention is further illustrated by way of the following non limiting examples.
11

EXAMPLE 1
Preparation of sodium salt of 2,6-bis(4,6-dimethoxypyrimidin-2-yloxy) benzoic acid
at a pKa in the range of 6.0 to 6.5
In a clean and dry flask, 1.54 g of 2,6-dihydroxy benzoic acid and 0.060 g of tetra butyl ammonium bromide as phase transfer catalyst was taken along with toluene solvent. 0.6 g of sodium hydroxide in fine prill form was added while stirring at reflux temperature for 1- 5 hrs to bring the pKa of the reaction mass to about 6.0 to 6.5 and then 2-methylsulfonyl-4,6-dimethoxy pyrimidine was added and the mixture further reacted with stirring for 12 to 18 hours to obtain the salt of 2,6-bis(4,6-dimethoxypyrimidin-2-yloxy ) benzoic acid. The reaction mass was filtered to recover the unreacted raw material and washed and dried to obtain the purified product. The salt was obtained in yield of 10%.
EXAMPLE 2
Preparation of sodium salt of 2,6-bis(4,6-dimethoxypyrimidin-2-yloxy ) benzoic acid
at a pKa in the range of 7.5 to 9.0
In a clean and dry flask 1.54 g of 2,6-dihydroxy benzoic acid and 0.060 g of tetra butyl ammonium bromide as phase transfer catalyst was taken along with toluene solvent. 1.2 g of sodium hydroxide in fine prill form was added while stirring and maintaining the temperature at 80°C for 1 to 5 hrs to bring the pKa of the reaction mass in the range of 7.5 to 9.0 and then 2-methylsulfonyl-4, 6-dimethoxy pyrimidine was added and the mixture further reacted with stirring for 12 to 18 hours to obtain the salt of 2,6-bis(4,6-dimethoxypyrimidin-2-yloxy) benzoic acid. The reaction mass was filtered to recover the
12

unreacted raw material and washed and dried to obtain the purified product. A high yield of the product was obtained ( 75 % ). The purified product was dissolved in water to get a known concentration which is suitable for spray application.
EXAMPLE 3
Preparation of sodium salt of 2,6-bis(4,6-dimethoxypyrimidin-2-yloxy ) benzoic acid
at a pKa in the range of 10.0 to 10.5
In a clean and dry flask 1.54 g of 2, 6-dihydroxy benzoic acid and 0.060 g of tetra butyl ammonium bromide as phase transfer catalyst was taken along with toluene solvent. 1.8 g of sodium hydroxide in fine prill form was added while stirring at reflux temperature for 1- 5 hrs to bring the pKa of the reaction mass to about 10.0 tol0.5 and then 2-methylsulfonyl-4, 6-dimethoxy pyrimidine was added and the mixture further reacted with stirring for 12 to 18 hours to get the salt of 2,6-bis (4,6-dimethoxypyrimidin-2-yloxy ) benzoic acid. The reaction mass was filtered to recover the unreacted raw material and washed and dried to obtain the purified product.
As discussed in the foregoing, the process of the invention (as exemplified by Example 2 ), wherein the pKa in the range of 7.5 to 9.0 is maintained, results in pyrimidynyloxy benzoic acid salt in high yield of 75%. At pKa values higher than 9.0 (as employed in the experiment of example 3) or at a pKa value lower than 7.5 (as employed in the experiment of example 1), the yield of the salt is substantially lower. Higher yields would result in increased productivity, easier isolation and lesser purification procedures.
13

Further, in the process of the invention the reactants are recycled and reused. Thus, there is savings in the cost and the overall efficiency is improved.
The above description is illustrative only and is not limiting- The invention is defined by the claims that follow and their full range of equivalents.
14

We claim:
1. A process for synthesis of a herbicidally active salt of pyrimidinyloxy benzoic acid having the formula

in high yields, wherein M+ is an alkali metal ion or an ammonium ion, the process comprising reacting a hydroxy substituted benzoic acid with a pyrimidine in the presence of a phase transfer catalyst, the reaction being carried out at a temperature in the range of 50 to 110°C in the presence of an inert organic solvent taken in a quantity of 4 to 5 liters per mole of any of the reactants and at a hydroxyl ion concentration required to maintain a pKa in the range of 7.5 to 9.0.
2. The process as claimed in claim 1 wherein the process is carried out in a single stage.
15

16
3. The process as claimed in any one of the claims 1 or 2 wherein the hydroxyl ion concentration is maintained by an alkali metal hydroxide.
4. The process as claimed in claim 3 wherein the metal hydroxide is sodium hydroxide.
5. The process as claimed in claim 4 wherein the sodium hydroxide is in the prill form.
6. The process as claimed in anyone of the claims 1 to 5 wherein the pyrimidine is 2-methyl suphonyl- 4, 6-dimethoxy pyrimidine.
7. The process as claimed in any one of the claims 1 to 6, wherein the phase transfer catalyst is selected from quaternary ammonium salts, polyethylene glycols and crown ethers.
8. A herbicidally active salt of pyrimidinyloxy benzoic acid having the formula,

wherein M is an alkali metal ion or an ammonium ion, the salt being synthesized by the process as claimed in any one of the claims 1 to 7.
9. A herbicidal composition comprising the salt as claimed in claim 8.
10. A method of killing weeds, the method comprising spraying the composition
as claimed in claim 9.
Dated this 14th day of August 2008

(Jose M A)
ofKhaitan&Co
Agent for the Applicants
17

Documents:

1729-MUM-2008-ABSTRACT(28-12-2011).pdf

1729-MUM-2008-ABSTRACT(30-3-2011).pdf

1729-MUM-2008-ABSTRACT(COMPLETE)-(14-8-2008).pdf

1729-MUM-2008-ABSTRACT(GRANTED)-21-3-2012).pdf

1729-mum-2008-abstract.doc

1729-mum-2008-abstract.pdf

1729-MUM-2008-CANCELLED PAGES(26-12-2011).pdf

1729-MUM-2008-CLAIMS(AMENDED)-(26-12-2011).pdf

1729-mum-2008-claims(amended)-(30-3-2011).pdf

1729-MUM-2008-CLAIMS(GRANTED)-(21-3-2012).pdf

1729-mum-2008-claims.doc

1729-mum-2008-claims.pdf

1729-MUM-2008-CORRESPONDENCE(20-12-2011).pdf

1729-MUM-2008-CORRESPONDENCE(23-8-2011).pdf

1729-MUM-2008-CORRESPONDENCE(24-9-2008).pdf

1729-MUM-2008-CORRESPONDENCE(28-12-2011).pdf

1729-MUM-2008-CORRESPONDENCE(30-3-2012).pdf

1729-MUM-2008-CORRESPONDENCE(31-5-2012).pdf

1729-MUM-2008-CORRESPONDENCE(IPO)-(21-3-2012).pdf

1729-mum-2008-correspondence.pdf

1729-mum-2008-description(complete).doc

1729-mum-2008-description(complete).pdf

1729-MUM-2008-DESCRIPTION(GRANTED)-(21-3-2012).pdf

1729-MUM-2008-FORM 1(24-9-2008).pdf

1729-MUM-2008-FORM 1(30-3-2011).pdf

1729-mum-2008-form 1.pdf

1729-mum-2008-form 13(24-9-2008).pdf

1729-mum-2008-form 13(30-3-2011).pdf

1729-MUM-2008-FORM 18(24-9-2008).pdf

1729-MUM-2008-FORM 2(GRANTED)-(21-3-2012).pdf

1729-MUM-2008-FORM 2(TITLE PAGE)-(26-12-2011).pdf

1729-MUM-2008-FORM 2(TITLE PAGE)-(30-3-2011).pdf

1729-MUM-2008-FORM 2(TITLE PAGE)-(COMPLETE)-(14-8-2008).pdf

1729-MUM-2008-FORM 2(TITLE PAGE)-(GRANTED)-(21-3-2012).pdf

1729-mum-2008-form 2(title page).pdf

1729-mum-2008-form 2.doc

1729-mum-2008-form 2.pdf

1729-MUM-2008-FORM 26(24-9-2008).pdf

1729-mum-2008-form 3.pdf

1729-MUM-2008-MARKED COPY(26-12-2011).pdf

1729-MUM-2008-MARKED COPY(30-3-2011).pdf

1729-MUM-2008-OTHER DOCUMENT(15-2-2012).pdf

1729-MUM-2008-REPLY TO EXAMINATION REPORT(30-3-2011).pdf

1729-MUM-2008-REPLY TO HEARING(15-2-2012).pdf

1729-MUM-2008-REPLY TO HEARING(26-12-2011).pdf

1729-mum-2008-specification(amended)-(24-9-2008).pdf

1729-MUM-2008-SPECIFICATION(AMENDED)-(26-12-2011).pdf

1729-MUM-2008-SPECIFICATION(AMENDED)-(30-3-2011).pdf

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Patent Number

251510

Indian Patent Application Number

1729/MUM/2008

PG Journal Number

12/2012

Publication Date

23-Mar-2012

Grant Date

21-Mar-2012

Date of Filing

14-Aug-2008

Name of Patentee

GODREJ AGROVET LTD

Applicant Address

PIROJSHANAGAR, EASTERN EXPRESS, HIGHWAY, VIKHROLI EAST, MUMBAI,

Inventors:

#	Inventor's Name	Inventor's Address
1	VYAS BRAHMANAND AMBASHANKAR	GODREJ AGROVET LTD, PIROJSHANAGAR, EASTERN EXPRESS, HIGHWAY, VIKHROLI EAST, MUMBAI-400079,
2	IYER RAMASWAMY,	GODREJ AGROVET LTD, PIROJSHANAGAR, EASTERN EXPRESS, HIGHWAY, VIKHROLI EAST, MUMBAI-400079,
3	GODREJ NADIR BURJOR	GODREJ AGROVET LTD, PIROJSHANAGAR, EASTERN EXPRESS, HIGHWAY, VIKHROLI EAST, MUMBAI-400079,
4	WAGHMARE SAMSON LUCAS	GODREJ AGROVET LTD, PIROJSHANAGAR, EASTERN EXPRESS, HIGHWAY, VIKHROLI EAST, MUMBAI-400079,
5	MISTRY KEKI BAMANSHAW	GODREJ AGROVET LTD, PIROJSHANAGAR, EASTERN EXPRESS, HIGHWAY, VIKHROLI EAST, MUMBAI-400079,

PCT International Classification Number

C07D239/60; A01N43/54; A01N43/78

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA