Silicon-carbon unsaturated compounds. 63. The formation of silacyclopropenes from thermal reactions of acylpolysilanes with bis(silyl) acetylenes

The cothermolysis of pivaloyl- and adamantoyltris(trimethylsilyl)silane with bis(trimethylsilyl)acetylene, bis(dimethylphenylsilyl)acetylene, and bis(methyldiphenylsilyl)acetylene afforded the respective adducts, silacyclopropenes, probably via isomerization of [2 + 2] cycloadducts arising from the reactions of silenes formed thermally from acylpolysilanes with bis(silyl)acetylenes. Thermolysis of the silacyclopropene formed from pivaloyltris(trimethylsilyl)silane and bis(trimethylsilyl)acetylene with 2,3-dimethyl-1,3-butadiene gave a 3,4-dimethyL-1-silacyclopent-3-ene derivative.