New chemistry of diazafulvenium methides: one way to pyrazoles

摘要

Diazafulvenium methides generated from the solution pyrolysis of pyrazolo[1,5-c][1,3]thiazole-2,2-dioxides participate in [8 pi+2 pi] cycloadditions giving pyrazolo[1,5-a]pyridine derivatives. 1-Methyl-diazafulvenium, generated under flash vacuum pyrolysis reaction conditions, undergoes an intramolecular sigmatropic [1,8]H shift giving 1-vinyl-1H-pyrazoles. (c) 2005 Elsevier Ltd. All rights reserved.