Efficient tautomerization hydrazone-azomethine imine under microwave irradiation. Synthesis of [4,3′] and [5,3′]bipyrazoles
作者:Ana Arrieta、José Ramón Carrillo、Fernando P. Cossío、Angel Díaz-Ortiz、María JoséGómez-Escalonilla、Antonio de la Hoz、Fernando Langa、Andrés Moreno
DOI:10.1016/s0040-4020(98)00798-4
日期:1998.10
Microwave irradiation induces the thermal isomerization of pyrazolyl hydrazones to the corresponding azomethine imines which undergo 1,3-dipolar cycloaddition with electron-poor dipolarophiles in a few min with good yields. By classical heating, several dipolarophiles do not react in comparable reaction conditions. Regiochemistry of bipyrazoles obtained from unsymmetrical dipolarophiles has been inferred by spectroscopic experiments. (C) 1998 Elsevier Science Ltd. All rights reserved.