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 vari ety of silacycles depending upon the alkyne. When terminal and electron-poo r alkynes (DMAD and methyl 2-butynoate) are employed, silole formation is f avored. Silirenes are formed preferentially when more electron-rich interna l alkynes are involved. Control experiments provide evidence that palladium (0) species are the active catalysts. By evaluation of product distribution s in these reactions, a catalytic cycle that accounts for the production of all silacycles can be proposed.