Electrolytic reduction of dichloromethylphenyl-, dichlorodiphenyl-, dichlorodi-o-tolyl-, and dichlorodi-p-tolylsilanes in the presence of 2,3-dimethylbutadiene afforded 1-methyl-1-phenyl-, 1,1-diphenyl-, 1,1-di-o-tolyl-, and 1,1-di-p-tolyl-3,4-dimethyl-1-silacyclopent-3-ene, respectively, while the similar reaction of chloromethyldiphenylsilane with 2,3-dimethylbutadiene afforded 1-(methyldiphenylsilyl)- and 1,4-bis(methyldiphenylsilyl)-2,3-dimethyl-2-butene. A reaction mechanism leading to these products has been discussed.