Preparation of 44benzoylpyrazole derivative

NEW MATERIAL:4-Benzoylpyrazole derivatives of formula I (R1, R2 are 1-3C straight-chained or branched alkyl; Y is O, S) or their salts. EXAMPLE:1,3-Dimethyl-4-(2,4-dichlorobenzoyl)-5-mercaptopyrazole. USE:Herbicide, whitening weeds to death. PREPARATION:A compound of formula V (X is halogen) is heated along with an alkali metal hydroxide as sodium hydroxide or potassium hydroxide or an alkali metal hydrosulfide as sodium hydrosulfide to form the objective compound of formula I. Further, when necessary, the resulting product is converted to the corresponding salt of alkali metal, ammonium or mineral acid. The compound of formula I can tautomerize to compounds of formula II-IV.