Tricyclazole is described and claimed in US publications.

4,064, 261 issued 20 sept. 1977.

984,288 issued 22 Jan. 1980 in Korean patent.

5,132 issued 7 Aug. 1976 in Taiwanese patent.

N, 19543 issued 13 oct. 1977.

US appl. 764026 issued in 1987.

And Japan Kokai JP 8 267,586 issued in 1982.

Japan Kokai JP 8267, 586 issued in 1982.

Reub. Korea KR 9,615, 035 issued in 2000 All these patents illustrate various processes for preparing Tricyclazole which prosseses are not advantageous and environmentally safe as is the present invention.

SUBSTITUTE SHEET (RULE 26) The present inventors conducted subject inventive process research on an industrially useful method for the production of Tricyclazole, from 2-Amino-4-methyl benzothiazole as a raw material and found out an industrial method giving high yield of high purity, with high productivity and most importantly environmental and man-power safety as compared to conventional methods and this led to present invention.

Conventional Techniques.

Patent USP 764,026 has mentioned a method of production Of Tricyclazole from 2-amino-4-methyl benzothiazole in one step without isolating Hydrazino intermediate in same reactor in 86-93.1 % yield of 98. 7 % Purity.

The superiority of present process over reported one is that final product is isolated in total aqueous slurry form without contamination of effluent hazard solvents. Reported method involved the isolation of product in Xylene-water phase involving potential hazards in filtration stage with suspected contamination of solvent in the environment. it is yet another object of this invention.

The present process yields consistent yield of 94-96 % with > 98 % purity by Gas Chromatographic method.

In patent Repub. Korea KR 9,615, 035 Tricyclazole is prepared from isolated 2-Hydrazino-4-methyl benzothiazole using conc. Sulphuric acid as a acid promotor catalyst.

In envisaged method p-Toluene sulphonic acid is utilised as a Effective acid promotor catalyst and is generally preferred to sulphuric acid because it is less damaging to the reactants and is solid (handling) to give highly pure product free from potential by-product impurities. p-Toluene sulphonic acid has been extensively used as Viscosity Reducer, surfactant, acid promotor, accelarator and cyclodehydration catalyst.

The problem this invention sousht to solve.

In the conventional methods the yields are low with concomittant formation of irreressible impurities and large quantity of solvent has to be handled during isolation of final product and from environmental & human safety point, these methods can not be said to be satisfactory industrial method.

Method of this invention is an industrial useful method that does not Possess the above defects. As catalyst is used in the reaction, the entire product remains in the suspension form even after complete removal of xylene solvent in the final stages of the process and can be conveniently pumped into water to separate the final product in slurry form which can be easily filtered or centrifused. Further use of efficient catalyst has minimised or eliminated impurities formation.

Detailed description of the invention.

This invention is concerned with the production of agrochemical namely 5-methyl-1,2, 4 triazol [3,4-b] benzothiazole, well known systemic Fungicide for the control of piricularia Oryzae, the causative organism of rice blast from raw material 2-Amino 4-methyl benzothiazole.

The improved process involves one pot reaction involving two steps.

In the first step of the process 2-amino-4-methyl benzothiazole is reacted with 80 % commercial Hydrazine hydrate in the presence of hydrochloric acid and Ethylene glycol. The concentration of AMBT is approximately 1 gm mole Per 700 ml of ethylene glycol and 3 gm mole of Hydrazine hydrate. The reaction Mixture is heated under reflux at 115-120° C for 3-4 hrs. The reaction is monitered by Gas chromatography for the absence of raw material AMBT. when reaction has gone as far as is desired, the reaction mixture is cooled to 90° C and Xylene in the range of 400 ml per gm mole of AMBT is added. The mixture is further cooled to 30 ° C. Agitation is stopped. The layers are seperated. Ethylene glycol layer is seperated and recycled in the later batch. Recycled ethylene glycol is analysed for Hydrazine hydrate and Hydrochloric acid contents and taken into account when recycle process is used. 2-Hydrazino-4-methyl benzothiazole containing Xylene layer is then washed with water. Xylene layer is neutralised with sodium carbonate.

The neutralised mixture is distilled to remove water and ethylene glycol. Seperated Xylene is returned to the reaction mixture. Xylene-water mixture is removed at atm. Press. at 100-110°C. While Xylene-Ethylene glycol is isolated under reduced pressure at about 100 ° C. Recovered ethylene glycol is reused in future Process.

To the Xylene-HBT slurry is added an excess amount of formic acid, preferably 5 moles of formic acid per mole of AMBT and 1 % p-Toluene sulphonic acid as acid promotor catalyst. the reaction is carried out for 3-4 hrs. until HBT has been completely converted into Tricyclazole, as monitered by Gas chromatography. During reaction excess of Xylene and formic acid is azeotropically recovered and recycled in the process. The contents of the vessel is cooled somewhat and 200-250 ml of Xylene per gram mole of product is added The mixture is reheated and azeotropic distillation is carried out to remove Substancially remaining formic acid to final liquid temp. of about 135-140 ° C at ambient pressure. at this temp. heating is continued till all Xylene being distilled out.

At this point the contents of the flask are in thick molten Flowable stirrable mass, probably through use of p-toluene sulphonic acid catalyst which has got distinguished property of surfactant & viscosity reducer. The mixture is cooled to 115-120 °C and pumped into precooled water under vigorous stirring. The product is centrifused and washed with water and Xylene to achieve desired purity.

The washed solids are dried in Rotary vaccume evaporator at 90-100 ° C.

Further it is true that ethylene glycol, Xylene, Most of the excess Hydrazine hydrate and Hydrochloric acid can be recycled. Formic acid recovered from the process can be reconstituted with 98 % commertial formic acid to be used in future lots.

Typically when process is operated according to the preferred conditions discussed above the yield will be about 94-96 % of the theoritical yield based on the amount of AMBT & product will be 98-99 % pure.

SUBSTITUTE SHEET (RULE 26) Application Example To a suitable glass lined reactor, equipped with heating, Cooling Jacket, an agitator, a condenser, condensate return and collection valves, seperator is charged 600 kg. of recycled and/or fresh Ethylene Glycol, 75 lit. of Coc. Hydrochloric acid, 120 kg. AMBT, and 50 lit. of NXZ defoamer. Mixture is heated to 70-75 ° C and 154. 5 kg. of 80 % Hydrazine hydrate is added in 1 hrs. it is then further heated to about 115-120°C and maintained for about 3-4 hrs.. The reaction is continued and monitered by gas chromatography till the absence of AMBT The mixture is cooled to 90 ° C and 300 lit. of Xylene is added. The agitator is stopped. and allowed to stand 1 hrs. Lower Ethylene Glycol layer is removed to be recycled in subsequent batch.

To the Xylene-Hydrazine Hydrate intermediate 150 lit. of water is added and stirred for 15 min. Lower layer is removed.

To the washed slurry 0.86 kg of sodium carbonate is added. and suspension is heated to reflux temp. of 110-115'C when azeotrope Xylene/water starts distilling out. Xylene layer is seperated in seperator and returned to the vessel.

Azeotropic distillation is continued till substancially all of the water has been removed. from the mixture. About 300 mm of vaccume is applied to the reactor at 110-115°C when Xylene/Ethylene Glycol starts seperating out. Heating is continued till no more Ethylene Glycol distills out. The vaccume is disconnected and the liquid temp. is SUBSTITUTE SHEET (RULE 26) allowed to cool at 90-100° C. Xylene recovered during process is returned to the Reactor and Ethylene Glycol is held for reuse.

To the slurry with agitation 1 kg. Of p-Toluene sulphonic acid Catalyst in 2 kg. of 98% Formic acid is added in 15 min. 138 kg. of 98% Formic acid is then added during I hrs. The contents are heated to boiling at 110°C. at this temp. Xylene/formic acid starts azeotropically distills out. Xylene is recycled.

Formic acid is returned to the reactor. Azeotropic distillation is continued till complete removal of Xylene. The contents are maintained atll5-120°C for 3-4 hrs. till completion of reaction, as determined by Gas chromatography for absence of Hydrazin intermediate. During this time most of the formic acid is distilled out. and can be recycled for reuse.

The mixture is cooled to 100 ° C and 150-200 lit. of Xylene is added. distillation is continued till temp. of about 140 ° C and maintained till time when condensate is substantially pure Xylene. Most of the xylene is removed for recycling process. The heating is continued till no more Xylene distills out.

The reaction mass is cooled to 120 ° C and molton slurry is pumped into another suitable agitated vessel containing about 500 lit. of precooled water. The mixture is stirred for 1-2 hrs. at ambient temp. to dissolve all inorganic impurities.

The slurry is filtered through basket centrifuge to collect solid product.

The product is washed with 2 x 100 lit. water and some Xylene. Wet Tricylazole is SUBSTITUTE SHEET (RULE 26) dried in rotary vaccume evaporator at 100° C to get dried mass having < 0.5 % moisture content.

The product was 134.6 kg. Of Tricyclazole (Yield 96 %), as described at the beginning of the document, which was found have purity of 98.6 % by Gas chromatography.