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
Single stage process for the synthesis of herbicidally active salt of pyrimidinyloxybenzoic acid
APPLICANTS
Godrej Agrovet Limited, Pirojshanagar, Eastern Express Highway, Vikhroli East, Mumbai -400079, Maharashtra, India, an Indian company
INVENTORS
Raut Sanjeev Daulat ,Waghmare Samson Lucas, Ramaraj Velaswamy Munuswamy, Vyas Brahmanand Ambashankar, 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
This invention relates to a single stage process for the synthesis of herbicidally active salt of pyrimidinyloxy benzoic acid.
This invention also relates to the herbicidally active salt of the pyrimidinyloxy benzoic acid, herbicidal composition thereof and 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 pyrimidyl compound. Yield of the pyrimidine derivatives obtained by the above method is 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.
In our Indian patent application No 1729/MUM/2008 filed on 14 August 2008, we have described a process for the synthesis of herbicidally active salt of pyrimidinyloxy benzoic acid of the following formula:


in high yields, wherein M' is an alkali metal ion or an ammonium ion. The process comprises reacting a hydroxy substituted benzoic acid with a pyrimidine in the presence of a phase transfer catalyst at 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, namely hydroxyl substituted benzoic acid and pyrimidine and at a hydroxyl ion concentration required to maintain a pKa in the range of 7.5 to 9.0.
DETAILED DESCRIPTION OF THE INVENTION
It has been found out by us after extensive research and experimentation that the yield of the herbicidally active salt of pyrimidinyloxy benzoic acid is substantially further increased by carrying out the reaction of the hydroxyl substituted benzoic acid with pyrimidine in the presence of the phase transfer catalyst and organic solvent at a higher temperature of 80-140°C and using the organic solvent in a reduced molar ratio of 1-2 litres per mole of one of the reactants namely hydroxyl substituted benzoic acid and pyrimidine.

According to the invention there is thus provided a single stage process for the synthesis of herbicidally active salt of pyrimidinyloxy benzoic acid of the following formula:

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 and an inert organic solvent and at a hydroxy1 ion concentration required to maintain a pKa in the range of 7.5 to 9.0, wherein the reaction is carried out at 80 to 140°C and the organic solvent is taken in the molar ratio of 1 to 2 litres per mole of the hydroxy 1 substituted benzoic acid or pyrimidine.
Advantageously, the reaction of the hydroxyl substituted benzoic acid with pyrimidine is carried out in a single stage. The hydroxyl ion concentration is maintained with an alkali metal hydroxide, alkali metal alkoxide or alkali metal carbonate. The alkali metal hydroxide, alkali metal alkoxide or alkali metal carbonate is selected from sodium or potassium hydroxide, sodium methoxide, potassium tertbutoxide or sodium or potassium carbonate. Preferably, the hydroxyl ion concentrated is maintained with sodium or potassium hydroxide, preferably sodium or potassium hydroxide prills. Preferably, the pyrimidine is 2-methyl suphonyl- 4, 6-dimethoxy pyrimidine. Preferably, the hydroxyl

substituted benzoic acid is 2, 6-dihydroxy benzoic acid. The phase transfer catalyst is selected from quaternary ammonium salts, polyethylene glycols, crown ethers or quarternary phosphonium salts selected from tertbutyl ammonium chloride, tertbutyl ammonium bromide, tetra butyl ammonium hydrogen sulphate or ethyl triphynyl phosphorium bromide and is preferably tetrabutyl ammonium chloride. The solvent is selected from xylene, benzene, toluene, dimethyl formaldehyde, dimethyl sulphoxide, methylpyrolidone, tetrachloroethylene or chlorobenzene and is preferably toluene or xylene.
According to the invention there is also provided the herbicidally active salt of the pyrimidinyloxy benzoic acid of the above formula synthesized by the above process; a herbicidal composition comprising the salt of the pyrimidinyloxy benzoic acid; and a method of killing weeds by spraying the herbicidal composition.
According to the invention the reaction between the hydroxy 1 substituted benzoic acid with pyrimidine is carried out at a higher temperature of 80-140°C and the organic solvent is taken in the reduced molar ratio of 1-2 liters per mole of the hydroxyl substituted benzoic acid or pyrimidine. As a result of this, the rate of the reaction is accelerated and the concentration of the reactants per unit volume of the reaction mixture is increased. This increases the collision between the particles of the reactants so as to increase the efficiency of the reaction and yield and productivity. Loss and wastage of the reactants are reduced. As the reaction volume is reduced, it is easy and convenient to

handle and control the reaction. Reaction time is also reduced as it is a single stage reaction.
The following examples are illustrative of the invention but not limitative of the scope thereof:
Example 1
5 g of 2, 6-Dihydroxy benzoic acid and 0.5 g of tetra butyl ammonium bromide-were taken along with xylene (0.1 litre). 5.64 g of Potassium hydroxide prills was added to the reaction while stirring at reflux temperature for 1. 5 hrs to bring the pka of the reaction mass to 7.5 to 9.0. 2-Methylsulfony 1-4, 6-dimethoxy pyrimidine was added to the reaction and the reaction mixture was further heated at 80 to 140°C with stirring for 8 hrs 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 the solid residue was washed with 0.05 litre and purified by crystallization in ethyl acetate. The residue was dried at 80°C to get purified product. The yield was high (85%) as very little amount of unreacted reactants was recovered back during the filtration.
The purified product is dissolved in water to get the desired concentration for spraying on crop plants.

Example 2
5 g of 2,6-Dihydroxy benzoic acid and 0.5 g of tetra butyl ammonium hydrogen sulphate were taken along with dimethyl formamide (0.1 liters). 4.02 g of Sodium hydroxide Prills was added to the reaction while stirring at reflux temperature for 1. 5 hrs to bring the pka of the reaction mass to 7.5 to 9.0 2-Methylsulfonyl-4, 6-dimethoxy pyrimidine was added to the reaction and the reaction mixture was further heated at 80 to 140 C for 8 hrs to get the salt of the 2, 6-bis (4, 6-dimethoxypyrimidin-2-yloxy) benzoic acid. The reaction mass was filtered to recover the unreacted raw material and the residue was washed with 0.05 litre and purified by crystallization in acetonitrile. The residue was dried at 80°C to get purified product. The yield was high (85 %) as very little amount of unreacted reactants was recovered back during the filtration
The purified product is dissolved in water to get the desired concentration for spraying on crop plants.
Example 3
5 g of 2,6-Dihydroxy benzoic acid and 1.0 g of tetra butyl ammonium chloride were taken along with toluene (0.1 litre ). 5.64 g of Potassium hydroxide prills was added to the reaction while stirring at reflux temperature for 1.5 hrs to bring the pka of the reaction mass to 7.5 to 9.0. 2-Methylsulfonyl-4,6-dimethoxy pyrimidine was added to the reaction and the reaction mixture was further heated at 80 to 140°C while stirring for 8 hrs 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 residue was washed with

0.05 litre and purified by crystallization in ethanol. The residue was dried at 80°C to get the purified product. The yield was high (85 %) as very little amount of unreacted reactants was recovered back during the filtration.
The purified product is dissolved in water to get the desired concentration for spraying on crop plants,
Example 4
5 g of 2,6-Dihydroxy benzoic acid and 1.0 g of tetra butyl ammonium bromide were taken along with xylene (0.1 litre). 4.02 g of Sodium hydroxide prills was added to the reaction while stirring at reflux temperature for l.Shrs to bring the pka of the reaction mass to 7.5 to 9.0. 2-Methylsulfonyl-4,6-dimethoxy pyrimidine was added to the reaction and the reaction mixture was further heated at 80 to 140°C while stirring for 8 hrs 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 the residue was washed with 0.05 litre and purified by crystallization in ethyl acetate. The residue was dried at 80°C to get the purified product. The yield was high (85%) as very little amount of unreacted reactants was recovered back during the filtration.
The purified product is dissolved in water to get the desired concentration for spraying on crop plants.

We Claim:
1. A single stage process for the synthesis of herbicidally active salt of pyrimidinyloxy benzoic acid of the following formula:

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 and an inert organic solvent and at a hydroxyl ion concentration required to maintain a pKa in the range of 7.5 to 9.0, wherein the reaction is carried out at 80 to 140°C and the organic solvent is taken in the molar ratio of 1 to 2 litres per mole of the hydroxyl substituted benzoic acid or pyrimidine.
2. The process as claimed in claim 1, wherein the hydroxyl ion concentration is maintained with an alkali metal hydroxide, alkali metal alkoxide or alkali metal carbonate.
3. The process as claimed in claim 2, wherein the alkali metal hydroxide, alkali metal alkoxide or alkali metal carbonate is selected from sodium or potassium hydroxide,

sodium methoxide, potassium tertbutoxide or sodium or potassium, potassium carbonate and is preferably sodium or potassium hydroxide and is still preferably sodium or potassium hydroxide prills.
4. The process as claimed in anyone of the claims 1 to 3, wherein the pyrimidine is 2-methyl sulphonyl- 4, 6-dimethoxy pyrimidine.
5. The process as claimed in any one of the claims 1 to 4, wherein the hydroxy 1 substituted benzoic acid is 2, 6-dihydroxy benzoic acid.
6. The process as claimed in any one of claims 1 to 5, wherein the phase transfer catalyst is selected from quaternary ammonium salts, polyethylene glycols, crown ethers or quaternary phosphonium salts selected from tertbutyl ammonium chloride, tertbutyl ammonium bromide, tetra butyl ammonium hydrogen sulphate or ethyl triphynyl phosphonium bromide and is preferably tetra butyl ammonium chloride.
7. The process as claimed in anyone of claims 1 to 6, wherein the solvent is selected from xylene, benzene, toluene, dimethyl formaldehyde, dimethyl sulphoxide, methylpyrolidone, tetrachloroethylene or chlrobenzene and is preferably toluene or xylene.
8. A herbicidally active salt of pyrimidinyloxy benzoic acid of the following formula:


wherein M+ is an alkali metal ion or an ammonium ion, synthesized by the process as claimed in any one of the claims 1 to 7.
9. A herbicidal composition comprising the salt of the pyrimidingloxy benzoic acid as claimed in claim 8.
10. A method of killing weeds by spraying the herbicidal composition as claimed in claim 9.