Patent CH-701924-B1 (CH)
Title: Preparation of trifluoromethylsulfenyl pyrazole for making fipronil involves halogenating halo-perhaloalkylaniline, isolating polyhalogenated aniline, diazotizing aniline, sulfinylating crude pyrazole, and oxidizing thio pyrazole compound
Inventor: GHARDA KEKI HORMUSJI
IPC: C07D231/44
Filed: 2010-10-26
Abstract: Preparation of trifluoromethylsulfenyl pyrazole involves a) halogenating aromatic compound to obtain polyhalogenated perhaloalkyl benzene; b) reacting in a polar solvent to give halo-perhaloalkyl aniline; c) reacting halo-perhaloalkylaniline compound with halogenating agent; d) isolating polyhalogenated perhaloalkylaniline compound; e) diazotizing isolated polyhalogenated aniline; f) reacting diazotized derivative with cyanoalkyl propionate derivative; g) isolating pyrazole compound; h) sulfinylating crude pyrazole compound; and i) oxidizing isolated thio pyrazole compound. Preparation of trifluoromethylsulfenyl pyrazole compound of formula (I) involves a) halogenating an aromatic compound of formula (II) to obtain polyhalogenated perhaloalkyl benzene compound of formula (III); b) reacting, in a polar solvent selected from N-methyl pyrrolidone, dimethyl sulfone, N,N-dimethylimidazolidinone and diphenyl sulfone, the compound of formula (III) with anhydrous ammonia in the presence of an alkali halide (preferably potassium fluoride) at 200-300[deg] C (preferably 235-250[deg] C), and a pressure of 20-50 (preferably 25-42) kg/cm 2>, to obtain a halo-perhaloalkyl aniline compound of formula (IV); c) reacting halo-perhaloalkylaniline compound (IV) with a halogenating agent selected from chlorine, sulfurylchloride, thionyl chloride and phosphorus pentachloride (preferably sulfurylchloride) in a solvent (preferably a chlorinated solvent selected from carbon tetrachloride, dichloromethane, chlorobenzene and o-dichlorobenzene), to obtain a product mixture containing polyhalogenated perhaloalkylaniline compound of formula (V); d) isolating polyhalogenated perhaloalkylaniline compound (V) preferably by distillation, from the product mixture; e) diazotizing isolated polyhalogenated aniline (V) with nitrosyl sulfuric acid in the presence of an acid solvent to form diazotized derivative of compound (V); f) reacting diazotized derivative with cyanoalkyl propionate derivative (preferably 2,3-dicyanoethyl propionate), and ammonia at 0-25[deg] C to obtain a reacted mixture containing pyrazole compound of formula (VII); g) isolating pyrazole compound from the reacted mixture with a halogenated aliphatic hydrocarbon solvent followed by evaporating the solvent to yield crude pyrazole compound (VII); h) sulfinylating crude pyrazole compound (VII) with a sulfinylating agent (preferably trifluoromethylsulfinylchloride) in an aliphatic hydrocarbon solvent to obtain a product mixture containing thio pyrazole compound of formula (IX), followed by isolating the thiopyrazole compound from the product mixture; and i) oxidizing the isolated thio pyrazole compound (IX) in a reaction medium comprising a oxidizing agent (preferably peroxide compound selected from hydrogen peroxide, tert-butyl hydrogen peroxide, benzoyl peroxide and sodium peroxide, especially hydrogen peroxide in the range of 0.8-1.2 molar equivalent); a solvent system; and a corrosion inhibitor (preferably boric acid) to yield a product mixture containing trifluoromethyl sulfenyl pyrazole compound (I). R 1 and R 2 : elements of halogen group; R 3 : perhaloalkyl; R : halogen (preferably chlorine); R 3 a : perhaloalkyl (preferably trifluoromethyl);and R 1 a and R 2 a : elements of halogen group (preferably Cl). [Image] [Image] [Image] ACTIVITY : Pesticide. No biological data given. MECHANISM OF ACTION : None given.