of electron-deficient alkenes with disilanes in acetonitrile gave silylated alkanes in high yields. The photosilylation occurred in a highly regioselective manner at the position β to the electron-withdrawing groups of the alkenes. With asymmetrically substituted disilanes and polysilanes, silyl groups bearing more bulky substituents were preferentially introduced to the alkenes. The photoreactions were
(thermodynamic control) should be abandoned, or at least seriously amended: kinetic factors appear to exert a primary influence on the regioselectivity of such reactions. Since the two major kinetic factors (i.e., electrophilic character of and steric hindrance at a given silicon atom) have opposite effects on the orientation of the reaction, it may happen that kinetic and thermodynamic control lead to the