Chemistry of Diazafulvenium Methides in the Synthesis of Functionalized Pyrazoles
作者:Teresa M. V. D. Pinho e Melo、Cláudio M. Nunes、Maria I. L. Soares、José A. Paixão、Ana Matos Beja、Manuela Ramos Silva
DOI:10.1021/jo070265x
日期:2007.6.1
The chemistry of diazafulvenium methides generated by the thermal extrusion of sulfur dioxide from 2,2-dioxo-1H,3H-pyrazolo[1,5-c] [1,3]thiazoles is described. The diazafulvenium methides unsubstituted at C-7 participate in [8 pi + 2 pi] cycloadditions giving pyrazolo-annulated heterocycles resulting from the addition across the 1,7-position. 1-Methyl-diazafulvenium methides and 7,7-dimethyl-diazafulvenium methides undergo intramolecular sigmatropic [1,8]H shifts giving vinyl-1H-pyrazoles.