NOVELTY - Forming trifluoromethylsulfinyl pyrazole compound involves: halogenating disubstituted phenylene compound to polyhalogenated perhaloalkyl benzene; reacting in polar solvent with anhydrous ammonia in presence of alkali halide to form halo-perhaloalkyl aniline compound; reacting with halogenating agent to form polyhalogenated perhaloalkylaniline compound; diazotizing; reacting with cyanoalkyl propionate derivative and ammonia to form substituted pyrazole compound; sulfinylating in aliphatic hydrocarbon to obtain thiopyrazole compound; and oxidizing in solvent with corrosion inhibitor.    USE - For preparation of trifluoromethylsulfinyl pyrazole compound (preferably 5-amino-(2,6-dichloro-4-(trifluoromethyl)phenyl)-4-((1(R,S)-trifluoromethyl)sulfinyl)-1H-pyrazole-3-carbonitrile (Fipronil)) (claimed), useful as a pesticide.    ADVANTAGE - The method provides a convenient and economically feasible process for preparing trifluoromethylsulfinyl pyrazole compounds (preferably Fipronil having high efficiency, low toxicity and low residue). The method allows for preparing Fipronil using easily and commercially available raw materials, and provides Fipronil in high yield and high purity of greater than 98%; where known commercial processes for the manufacture of Fipronil use corrosive and expensive chemicals such as trifluoroacetic acid, hydrogen peroxide and meta-chloroperbenzoic acid, in which trifluoroacetic acid is expensive and generally not used in large quantities, as well as meta-chloroperbenzoic acid is difficult to handle at commercial scale due to its un-stability and detonating effect. Also the raw material used such as 2,6-dichloro-4-trifluoromethylaniline are not easily available or made. In the method, the polyhalogenated perhaloalkyl benzene compound (II) is obtained in high yields and purity by chlorination of aromatic compound (II). Ammonolysis of compound (III) to obtain halo-perhaloalkylaniline compound (IV) is easier and facile as compared to that of para-chlorobenzotrifluoride and provides much higher conversions.    DETAILED DESCRIPTION - Preparation of a trifluoromethylsulfinyl pyrazole compound of formula (I) involves:    (A) halogenating an aromatic compound of formula (II) to obtain a 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 (III) with anhydrous ammonia in the presence of an alkali halide (preferably potassium fluoride) at (200-300, preferably 235-250) degrees C and a pressure of (20-50, preferably 25-42) kg/cm2 to obtain a halo-perhaloalkyl aniline compound of formula (IV);    (C) reacting the compound (IV) with a halogenating agent selected from chlorine, sulfuryl chloride, thionyl chloride and/or phosphorus pentachloride (preferably sulfuryl chloride) in a solvent (preferably a chlorinated solvent selected from carbon tetrachloride, dichloromethane, chlorobenzene and ortho-dichlorobenzene), to obtain a product mixture containing polyhalogenated perhaloalkylaniline compound of formula (V) (where R1 and R2 are preferably Cl);    (D) isolating the compound (V), preferably by distillation, from the product mixture;    (E) diazotizing the isolated polyhalogenated aniline compound (V) with nitrosyl sulfuric acid in the presence of an acid solvent to form a diazotized derivative of the compound (V);    (F) reacting the diazotized derivative of compound (V) with cyanoalkyl propionate derivative (preferably 2,3-dicyanoethyl propionate), and ammonia at 0-25 degrees C to obtain a reacted mixture containing pyrazole compound of formula (VI);    (G) isolating the pyrazole compound (VI) from the reacted mixture with a halogenated aliphatic hydrocarbon solvent followed by evaporating the solvent to yield crude pyrazole compound (VI);    (H) sulfinylating the crude pyrazole compound (VI) with a sulfinylating agent (preferably trifluoromethylsulfinyl chloride), in an aliphatic hydrocarbon solvent to obtain a product mixture containing a thiopyrazole compound of formula (VII), followed by isolating the thiopyrazole compound form the product mixture; and    (I) oxidizing the isolated thiopyrazole compound (VII) in a reaction medium comprising an oxidizing agent (preferably a peroxide compound selected from hydrogen peroxide, tert-butyl hydrogen peroxide, benzoyl peroxide and sodium peroxide; especially hydrogen peroxide) (0.8-1.2 molar equivalent), solvent system, and corrosion inhibitor (preferably boric acid), to yield a product mixture containing the trifluoromethylsulfinyl pyrazole compound (I).    R1 and R2=halo (preferably Cl);    R3=perhaloalkyl (preferably trifluoromethyl);    R'=halo (preferably Cl).