Palladium-Catalyzed Reactions of Di-tert-butylsiliranes with Electron-Deficient Alkynes and Investigations of the Catalytic Cycle

Siliranes undergo palladium-catalyzed reactions with alkynes to give a variety of silacycles depending upon the alkyne. When terminal and electron-poor alkynes (DMAD and methyl 2-butynoate) are employed, silole formation is favored. Silirenes are formed preferentially when more electron-rich internal alkynes are involved. Control experiments provide evidence that palladium(0) species are the active catalysts. By evaluation of product distributions in these reactions, a catalytic cycle that accounts for the production of all silacycles can be proposed.