Stereochemistry of Disilanylene-Containing Cyclic Compounds. Synthesis and Reactions ofcis- andtrans-1,2-Dimethyl-1,2-diphenyl-1,2-disilacyclopentanes

The Wurtz type coupling of a mixture of meso- and dl-1,4-bis(chloromethylphenylsilyl)butanes with lithium metal in the presence of a catalytic amount of dimethylphenylsilyllithium afforded cis- and trans-1,2-disilacyclohexane (1a and 1b) in a ratio of 4:6. Pure 1a and 1b obtained by fractional distillation reacted with diphenylacetylene in the presence of a platinum catalyst at 200 °C to give stereospecifically the respective cis- and trans-1,4-dimethyl-1,2,3,4-tetraphenyl-1,4-disilacyclooct-2-ene (2a and 2b). Under identical conditions, the reactions of 1a and 1b with 1-phenyl-1-propyne, 3-hexyne, and phenylacetylene also proceeded with stereospecificity to form similar adducts.