Silver-Catalyzed Silacyclopropenation of 1-Heteroatom-Substituted Alkynes and Subsequent Rearrangement Reactions

Silver phosphate-catalyzed silylene transfer from silacyclopropane 1 to 1-heteroatom-substituted alkynes resulted in alkoxy-, amino-, and alkylthiolate-substituted silacyclopropenes. Silver-catalyzed silylene transfer to 1-halo- and 1-sulfonyl-substituted alkynes led to insertion of silylene into the carbon−heteroatom bond. Attempts at copper-catalyzed insertion of carbonyl compounds into heteroatom-substituted silacyclopropenes led to rearrangement into silicon-substituted alkynes with a net silylene insertion into the carbon−heteroatom bond. Mechanistic studies were conducted utilizing crossover experiments. A mechanism involving transmetalation/elimination was supported by the observation of crossovers in double-labeling experiments for alkynyl sulfides, halides, and sulfones.