Ring-Chain Tautomerism of 3-Unsubstituted Trifluoromethyl-Containing N-Acyl-5-hydroxy-2-pyrazolines.

Derivatives having a 5-hydroxy-2-pyrazoline structure (III) are formed by reaction of hydrazides of aromatic and pyridine-carboxylic acids (II) with 4-ethoxy-1,1,1-trifluorobutenone (I).