Effects of Proximate Polar Groups on the Rates of Hydrosilylation

Article abstract of DOI:10.1021/jo00386a003

Endo-, exo-, and trans-2,3-disubstituted bicyclo<2.2.1>hept-5-enes were found to react with dimethylchlorosilane in the presence of a platinum catalyst to yield the corresponding 5-silyl derivatives.The reaction of the endo anhydride proceeded in high yield, although quite slowly.The exo anhydride was found to react faster than the analogous endo epimer.Furthermore, the endo N-phenylimide did not react under these conditions, while the exo N-phenylimide epimer reacted rapidly and in high yield.A similar ordering of reactivity was observed with the endo-, trans-, and exo-2,3-dicarbomethoxybicyclo<2.2.1>hept-5-enes.Silicon was found exclusively on the exo face of the bicycloheptyl skeleton, remote from substituents at the 2,3-positions.Purely steric arguments are insufficient to explain the anomalous reactivity of the endo anhydride and endo N-phenylimide.However, the reactivity differences can be rationalized in terms of field effects exerted by the electron-deficient anhydride and imide rings.