Alkylidenesilacyclopropanes derived from allenes: applications to the selective synthesis of triols and homoallylic alcohols.

Several alkylidenesilacyclopropanes were prepared by silver-mediated silylene transfer to allenes. Oxasilacyclopentanes derived from allenes were prepared with high regio- and diastereoselectivity by a two-step, one-flask silacyclopropanation/carbonyl insertion reaction. Triols and homoallylic alcohols were formed diastereoselectively by functionalizing the oxasilacyclopentanes. An optically active allene (>98% ee) was utilized to synthesize an enantiopure homoallylic alcohol in 96% ee.

Silylene oxonium ylides: di-tert-butylsilylene insertion into C-O bonds.

Allylic ethers undergo insertions of silylenes into C-O bonds to form allylic silanes. Silylene insertion into C-O acetal bonds was also observed. Formation of silylene ylide intermediates led to [1,2]-Stevens rearrangement products as well as [2,3]-sigmatropic products depending upon the steric environment of the starting allylic ether.