Palladium-catalyzed reactions of 1,1,2,2-tetraethyl-and 1,1,2,2-tetra(isopropyl)-3,4-benzo-1,2-disilacyclobut-3-ene with alkynes

Article abstract of DOI:10.1016/0022-328X(96)06160-8

The reactions of 3,4-benzo-1,1,2,2-tetra(isopropyl)-1,2-disilacyclobut-3-ene (2) with acetylene, phenylacetylene, 1-hexyne, and o-tolylacetylene in the presence of tetrakis(triphenylphosphine)palladium gave the respective 5,6-benzo-1,4-disilacyclohexa-2,5-dienes 3-6. Similar reactions of 2 with mesitylacetylene, trimethylsilylacetylene, and dimethylphenylsilylacetylene afforded 1-alkynyl(diisopropylsilyl)-2-(diisopropylsilyl)benzenes 7-9 arising from sp-hybridized C-H bond activation of acetylenes. The reactions of 3,4-benzo-1,1,2,2-tetraethyl-1,2-disilacyclobut-3-ene with mesitylacetylene, trimethylsilylacetylene, and dimethylphenylsilylacetylene produced 5,6-benzo-1,4-disilacyclohexa-2,5-dienes 10-12 as the sole product. The stoichiometric reaction of 2 with tetrakis(triphenylphosphine)palladium gave a yield of 3,4-benzo-2,2,5,5-tetra(isopropyl)-1-pallada-2,5-disilacyclopent-3-ene (A), arising from insertion of a palladium species into a silicon-silicon bond in 2.