1 2-ADDUCTS FROM SILYLENES AND 1,3-BUTADIENE

Photochemical generation of dimethylsilylene, methyl(phenyl)silylene a nd diphenylsilylene in the presence of high concentrations of 1,3-buta diene leads to the formation of 1-sila-3,4-divinylcyclopentanes as maj or products in addition to the anticipated 1-silacyclopent-3-enes. Als o obtained are the ene-reaction products from the silenes, formed by f ormal 1,3-silyl shifts in the bis(trimethylsilyl)arylsilanes that are employed as the photochemical precursors of MePhSi: and Ph(2)Si:. Evid ence is presented that both the divinylsilacyclopentanes and the silac yclopent-3-enes arise from vinylsilirane intermediates that can be tra pped by acetone, yielding stable 3,3-dimethyl-4-vinyl-1-sila-2-oxolane s.