Migration of an acyl group in the pyrazole system: synthesis of 1-acyl-3-hydroxy-1H-pyrazoles and related derivatives. A new preparation of N,N′-diacylhydrazines

Abstract

A new general method for the synthesis of 1-acyl-3-hydroxy-1H-pyrazoles 5a–f and related derivatives 5g–i starting from 4-ethoxymethylene-2-phenyloxazol-5(4H)-one (1) and hydrazides, 4-phenylsemicarbazide, 4-phenylthiosemicarbazide and benzyl carbazate in boiling dioxane is described. The method includes a migration of an acyl or related unit. The X-ray study and NMR spectroscopic examination confirmed the structure of the products. A one-pot synthesis of N,N′-diacylhydrazines from hydrazides by the assistance of oxazolone 1 is also presented.