The addition of terminal alkynes to dimesitylfluorenylidenegermane

Abstract

A variety of terminal alkynes were added to dimesitylfluorenylidenegermane, Mes2Ge=CR2 (where CR2 = fluorenylidene).The addition of phenylacetylene and 1-hexyne to Mes2Ge=CR2 gave a germacyclohexene via a cycloaddition where the germene acts as the 4π component and the alkyne as the 2π component.Through the use of a mechanistic probe, trans-(2-phenylcyclopropyl)-acetylene, the reaction was postulated to proceed through a concerted [2+4] cycloaddition.The addition of ethoxyacetylene to the germene produced both a [2+2] cycloadduct, a germacyclobutene, and a [2+4] cycloadduct, a germacyclohexene.The results of this study are compared to the results of the addition of alkynes to Mes2Ge=CHCH 2-t-Bu.© 2014 Published by NRC Research Press.