NICKEL-CATALYZED REACTIONS OF 3,4-BENZO-1,1,2,2-TETRAETHYL-1,2-DISILACYCLOBUT-3-ENE WITH CARBONYL-COMPOUNDS

The reaction of 3,4-benzo-1,1,2,2-tetraethyldisilacyclobut-3-ene (1) with benzaldehyde in the presence of a catalytic amount of Ni(PEt3)4 at 150-degrees-C afforded 5,6-benzo-1,1,4,4-tetraethyl-2-oxa-3-phenyl-1,4-disilacyclohex-5-ene in 75% yield. Similar nickel-catalyzed reaction of 1 with acetone gave 5,6-benzo-1,1,4,4-tetraethyl-3,3-dimethyl-2-oxa-1,4-disilacyclohex-5-ene, 1-[diethyl(isopropenyloxy)silyl]-2-(diethylsilyl)benzene,and 4,5-benzo-1,1,3,3-tetraethyl-2-oxa-1,3-disilacyclopent-4-ene (6) in 26%, 31%, and 24% yields, respectively. Treatment of 1 with acetophenone, pinacolone, and propiophenone afforded the respective adducts, 1-[diethyl[(l-phenylvinyl)oxy]silyl]-, 1-[[(l-tert-butylvinyl)oxy]diethylsilyl]-, and 1-[diethyl[(l-phenyl-1-propenyl)oxy]silyl]-2-(diethylsilyl)benzene, in 59%, 27%, and 70% yields, respectively, in addition to 6. Similar treatment of 1 with benzophenone produced 4 ,5-benzo-1,1,3,3-tetraethyl-2,2-diphenyl-1,3-disilacyclopent-4-ene and 6 in 20% and 57% yields, while with 4,4'-dimethylbenzophenone, 1 gave 4,5-benzo-1,1,3,3-tetraethyl-2,2-di(p-tolyl)-1,3-disilacyclopent-4-ene and 6 in 16% and 37% yields. The reaction of 1 with benzophenone in the presence of the nickel catalyst in refluxing cyclohexene gave 7,7-diphenylnorcarane and 6 in 39% and 57% yields.