New Strategy for the Construction of Carbocyclic Alkenyl Silanes: The Synthesis of 1,1,2,2-Tetramethyl-1,2-Disilacyclopent-3-ene

摘要

Cyclization of 1,2-bis(bromomethyl)-1,1-2,2-tetramethyldisilane, 2, with the dianion of methylphenylsulphone in tetrahydrofuran at -78 C produces the 4-phenylsulfphone substituted 1,2-disilacyclopentane derivative, 4, in 59% yield. Ring opening of 2 with potassium t-butoxide occurs quantitatively to provide 1-(t-butoxy)-2(-2-propenyl)-1,1,2,2-tetramethyl-disilane, 5. Addition of the monoanion of methylphenylsulphoxide to 2 in THF at -78 C provides the intermediate adduct, 7, which is cyclized at -78 C with addition of one equivalent of lithium diisopropylamide to provide the 4-phenylsulphoxide substituted 1,2-disilacyclopentane derivative, 6, in 30% yield from 2. Flash vacuum thermolysis of 6 at 100 C (.000001 torr) provides 1,1,2,2-tetramethyl-1,2-disilacyclopent-3-ene, 1, in 40% yield. Pentanes, Silanes, Cyclopentanes. (mjm)