A New Route to 1-Substituted Pyrazole-4-Carboxylic Acids

1-PHENYLPYRAZOLE-4-CARBOXYLIC acid has been hitherto most successfully synthesized by chloromethylation of 1-phenylpyrazole and subsequent oxidation of the 4-chloromethyl-1-phenylpyrazole1, or by hydrolysis of the 4-cyano derivative formed from the anti-oxime of 4-formyl-1-phenylpyrazole2. A synthesis of this acid has now been achieved by the hydrolysis of 4-cyano-1-phenylpyrazole formed by a Sandmeyer type reaction from 1-phenylpyrazole-4-diazonium chloride. Replacement of the pyrazole-4-diazonium group by nitrile has hitherto been unsuccessful3,6.