ニッケルならびにパラジウム触媒によるクロロシランの選択的分子変換

抄録

Industrially-produced chlorosilanes are cheap and abundant silicon feedstocks. To obtain various useful organosilicon compounds directly from these chlorosilanes, classical nucleophilic substitution reactions (Kipping method) with reactive organometallic reagents such as Grignard reagents and organolithium are often employed. In contrast, their direct catalytic transformation into beneficial organosilicon compounds remains challenging due to difficulty in cleaving the strong Si-Cl bond(s). To address this issue, we hypothesized that the activation of chlorosilanes with transition metal catalysts could be achieved with the cooperative assistance of Lewis acids by stabilizing the transition state or products. We initially developed Ni-catalyzed silyl-Heck reaction of chlorosilanes and styrenes. The aid of trimethylaluminum dramatically assisted silyl-Heck reaction to afford the corresponding alkenylsilanes. Successively, we also achieved the Ni-catalyzed cross-coupling reaction of chlorosilanes with trialkylaluminum species. Interestingly, the selective monoalkylation of dichlorosilanes was achieved to form various monochrolosilanes with a variety of alkyl substituents, which are useful raw materials for silicones. To further broaden the scope of this cross-coupling reaction, we then developed Pd-catalyzed cross-coupling reaction of chlorosilanes with dimethylaluminum chloride. The broader generality of di-, tri- and tetrachlorosilanes was revealed in the selective methylation to provide the corresponding methylmonochlorosilanes. Finally, we demonstrated computational study on the activation of Si-Cl bond by the cooperation of palladium and aluminum Lewis acid.