NICKEL-CATALYZED REACTIONS OF 3,4-BENZO-1,1,2,2-TETRAETHYL-1,2-DISILACYCLOBUTENE WITH AROMATIC-COMPOUNDS

The reaction of 3,4-benzo-1,1,2,2-tetraethyl-1,2-disilacyclobutene (1) with benzene in the presence of Ni(PEt3)4 gave 1-(diethylphenylsilyl)-2-(diethylsilyl)benzene (4a) in high yield. Similar reaction of 1 with toluene gave 1-[diethyl(3-methylphenyl)silyl]- and 1-[diethyl(4-methylphenyl)silyl]-2-(diethylsilyl)benzene (5a,b). The reaction of 1 with isopropylbenzene also produced the corresponding two regioisomers. With m-xylene, 1 afforded 1-[diethyl(3,5-dimethylphenyl)silyl]- and 1-[diethyl(2,4-dimethylphenyl)silyl]-2-(diethylsilyl)benzene, while the reaction of 1 with p-xylene gave 1-[diethyl(2,5-dimethylphenyl)silyl]-2-(diethylsilyl)benzene as a main product, in addition to 1-[diethyl(4-methylbenzyl)silyl]-2-(diethylsilyl)benzene as a minor product. Similar reaction of 1 with mesitylene gave 1-[diethyl(3,5-dimethylbenzyl)silyl]-2-(diethylsilyl)benzene. The nickel-catalyzed reaction of 1 with a 1:1 mixture of benzene and toluene afforded 4a, 5a, and 5b in 56, 22, and 9 % yields, while, with a 1:1 mixture of benzene and mesitylene, 4a was produced as the sole product.