Alkali metal,alkaline and acidic decomposition of silacyclopentadienes

1,1-Dimethyl-2,5-diphenyl-1-silacyclopentadiene and 1,1-dimethyl-2,3,4,5-tetraphenyl-1-silacyclopentadiene (X) are cleaved by sodium hydroxide as well as by hydrochloric acid to give trans, trans-1,4-diphenylbutadiene and cis, cis-1,2,3,4-tetraphenylbutadiene, respectively. Compound X, hexaphenylsilacyclopentadiene and 1-methyl-1,2,3,4,5-pentaphenyl-1-silacyclopentadiene, on treatment with potassium in 1,2-dimethoxyethane gave intensely red colored dianions which on quenching in moist tetrahydrofuran gave rise to α,α′-dibenzylstilbene. A pathway for the reaction is suggested.