Stereochemistry of disilanylene-containing cyclic compounds. Synthesis andreactions of cis- and trans-1,2-dimethyl-1,2-diphenyl-1,2-disilacyclopentanes

The Wurtz type coupling of a mixture of meso- and dl-1,3-bis(chloromethylph enylsilyl)propanes with sodium metal afforded a mixture of cis- and trans-d isilacyclopentanes (1a and 1b) in a ratio of 1:1. Pure la and Ib obtained b y fractional distillation reacted with molecular oxygen in the presence of AlBN stereospecifically to give the respective cis- and trans-cyclic siloxa nes (2a and 2b), with retention of configuration. The reactions of la and I b with MCPBA produced cleanly 2a and 2b in high yields, respectively. The p alladium-catalyzed reactions of la and Ib with phenylacetylene gave stereos pecifically cis- and trans-1,4-dimethyl-1,2,4-triphenyl-1,4-disilacyclohept -2-enes (3a and 3b), in high yields. Similar treatment of la and Ib with di phenylacetylene also proceeded with high stereospecificity to give cis- and trans-1,4-dimethyl-1,2,3,4-tetraphenyl-1 (4a and 4b), respectively. The re sults of an X-ray crystallographic study for products 4a and 4b are describ ed.