Synthesis of 1-substituted derivatives of 2,5-diphenylsilacyclopent-3-enesand 2,5-diphenylsilacyclopentanes

Synthesis of 1,1-disubstituted derivatives of 2,5-diphenylsilacyclopent-3-e nes and 2,5-diphenylsilacyclopentanes was investigated. 1,1-Disubstituted derivatives of 2,5-diphenylsilacyclopent-3-enes having di alkoxy, I-alkoxy-l-methyl, l-alkoxy-l-chloro, and l-alkyl-l-chloro were pre pared by one-pot reaction of (1E, 3E) -1,4-diphenylbuta-1,3-diene and dichl orosilanes in the presence of magnesium. 1,1-Dialkoxy derivatives were obta ined in about 80% yield, but I-alkyl-l-chloro derivatives were obtained und er 50% yield. Each silacyclopentenes was given as the mixture of trans and two cis isomers. 1,1-Dialkoxy derivatives were obtained as a trans rich for m and 1-alkyl-1-chloro derivatives were obtained as only cis isomer. Then t he hydrogenation of 1,1-disubstituted derivatives of 2,5-diphenylsilacyclop ent-3-enes by hydrogen gas in the presence of Pd-C gave the corresponding d erivatives of 2,5-diphenylsilacyclopentanes.