Transition-Metal Reactions of small-ring silicon compounds

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In this paper we report the transition-metal reactions of small-ring compounds containing silicon-silicon bond. The palladium-catalyzed reactions of pure cis-and trans-3, 4-benzo-1, 2-di(tert-butyl)-1, 2-dimethyl1, 2-disilacyclobut-3-ene (1a and 1b) with phenylacetylene and 1-hexyne produced stereospecifically cis-and trans-5, 6-benzo-1, 4-disilacyclohexa-2, 5-dienes.The Wurtz type coupling of a mixture of meso-and dl-1, 3-bis (chloromethylphenylsilyl) propanes with sodium metal afforded a mixture of cis-and trans-disilacyclopentanes (2a and 2b) in a ratio of 1 : 1.The palladium-catalyzed reactions of 2a and 2b with phenylacetylene gave stereospecifically cis-and trans-1, 4-dimethyl-1, 2, 4-triphenyl-1, 4-disilacyclohept-2-enes (3a and 3b), in high yields. Similar treatment of 2a and 2b with diphenylacetylene also proceeded with high stereospecificity to give cis-and trans-1, 4-dimethyl-1, 2, 3, 4-tetraphenyl-1, 4-disilacyclohept-2-enes (4a and 4b), respectively.The platinum-catalyzed … More reactions of 2a with terminal acetylenes such as phenylacetylene and 1-hexyne in a degassed sealed tube at 150℃ for 24h afforded cis-1, 4-dimethyl-1, 2, 4-triphenyl-1, 4-disilacyclohept-2-ene (5a) and cis-2-n-butyl-1, 4-dimethyl-1, 4-diphenyl-1, 4-disilacyclohept-2-ene (6a), respectively, arising from insertion of a triple bond in the acetylenes into a silicon-silicon bond. Similar reactions of 2b with phenylacetylene and 1-hexyne gave trans-1, 4-dimethyl-1, 2, 4-triphenyl-1, 4-disilacyclohept-2-ene (5b) and trans-2-n-butyl-1, 4-dimethyl-1, 4-diphenyl-1, 4-disilacyclohept-2-ene (6b), respectively. The platinum-catalyzed reactions of 2a and 2b with di-substituted acetylenes such as diphenylacetylene, 1-phenyl-1-propyne, and 3-hexyne gave the respective cis-and trans-1, 4-dimetnyl-1, 4-diphenyl-1, 4-disilacyclohept-2-ene derivatives with high stereospecificity. The nickel-catalyzed reactions of 2a and 2b with di-substituted acetylenes also proceeded with high stereospecificity to give the adducts as observed in the platinum-catalyzed reactions.The palladium-catalyzed reaction of 1, 1-dimethyl-2, 2-diphenyl-1, 2-disilacyclopentane (7) with phenylacetylene gave regiospecifically 4, 4-dimethyl-1, 1, 2-triphenyl-1, 4-disilacyclohept-2-ene (8) in 93% yield. Similar treatment of 7 with tert-butylacetylene and 1-hexyne also proceeded with high regiospecificity to give 2-tert-butyl-4, 4-dimethyl-1, 1-diphenyl-1, 4-disilacyclohept-2-ene (9) and 2-n-butyl-4, 4-dimethyl-1, 1-diphenyl-1, 4-disilacyclohept-2-ene (10) in 93% and 90% yields, respectively. The platinum-catalyzed reactions of 7 with phenylacetylene, tert-butylacetylene, and 1-hexyne afforded regiospecifically the same products as those obtained from palladium-catalyzed reactions in high yields. Less