Treatment of ethyl alpha-per(poly)fluoroalkyl acetates 1 or ethyl alph
a-iodo-beta-per(poly) fluoroalkyl acrylates 2 with hydrazine gives 3-h
ydroxy-5-per(poly)fluoroalkyl pyrazoles 3 in excellent yield. The effe
ct of halogens on the pert polyfluoroalkyl chain and the reaction cond
itions were studied.