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

The Wurtz type coupling of a mixture of meso- and dl-1,4-bis(chloromethylph enylsilyl)-butanes with lithium metal in the presence of a catalytic amount of dimethylphenylsilyl-lithium afforded cis- and trans-1,2-disilacyclohexa ne (1a and 1b) in a ratio of 4:6. Pure 1a and 1b obtained by fractional dis tillation reacted with diphenylacetylene in the presence of a platinum cata lyst at 200 degreesC to give stereospecifically the respective cis- and tra ns-1,4-dimethyl-1,2,3,4-tetraphenyl-1,4-disilacyclooct-2-ene (2a and 2b). U nder identical conditions, the reactions of 1a and 1b with 1-phenyl-1-propy ne, 3-hexyne, and phenylacetylene also proceeded with stereospecificity to form similar adducts.