Synthesis of 1‐(1,1‐dimethylethyl)‐1H‐pyrazole‐4‐carboxylate ester derivatives

Attempts to prepare ethyl 5‐cyano‐1‐(1,1‐dimethylethyl)‐1H‐pyrazole‐4‐carboxylate (7) by the reaction of the corresponding 5‐chloro derivative 1b with cyanide ion were unsuccessful. The chloro ester was synthesized from the corresponding amino ester la utilizing nonaqueous diazotization with nitrosyl chloride. An alternate process was developed which allowed the preparation of 7 from the corresponding 5‐methyl ester 3 in four steps. The structure of the N‐methylamide 8 synthesized from 7 was confirmed by X‐ray diffraction analysis.