Photochemistry of Trifluoromethyl Substituted 1‐Methylpyrazoles.

Abstract

Trifluoromethyl substitution on the pyrazole ring was found to enhance photoreactivity via the P 4 pathway which involves interchange of the N2-C3 ring atoms. Thus, 1-methyl-3-(trifluoromethyl)pyrazole (1) and 1-methyl-5-(trifluoromethyl)pyrazole (3) transposed with a P 4 /P 6 or P 4 /P 6 +P 7 ratio of 2.1:1. 1-Methyl-4-(trifluoromethyl)pyrazole (2) transposed regiospecifically by the P 4 transposition pathway. Compounds 2 and 3 were also observed to undergo photocleavage to yield enaminonitrile and enaminoisocyanide products.