1,3-Dipolar cycloadditions of silicon and tin alkynes and alkenes. Regiospecific synthesis of silyl and stannylpyrazoles and pyrazolines
作者:Ana M. González-Nogal、Mariola Calle、Purificación Cuadrado、Raquel Valero
DOI:10.1016/j.tet.2006.10.026
日期:2007.1
Silicon and tin 3-, 3,5-, and 3,4,5-metalated pyrazoles have been synthesized by 1,3-dipolar cycloadditions of silyl-, disilyl-, and silylstannyl acetylenes with N-phenylsydnone or trimethylsilyldiazomethane. On the other hand, 1- and 2-pyrazolines monometalated and dimetalated in different positions of the heterocycle have been prepared by reaction of vinylsilanes and vinylstannanes with the same 1,3-dipolar reagents. Other interesting products resulting from homologation were obtained by cycloaddition of trimethylsilyldiazomethane with beta-silyl enones and esters. Moreover, for the first time a 3-silylpyrazole has been converted into a 3-cyanopyrazole. (c) 2006 Elsevier Ltd. All rights reserved.