Electronic and steric effects of silyl groups in silicon-directed Norrish type cleavages

Sterically congested cis-2-(t-butyl)-3-(organosilyl)cyclohexanones were irradiated with UV light to give a mixture of Norrish type I and II products, as well as the corresponding trans-2-(t-butyl)-3-(organosilyl)cyclohexanones. In comparison with the trans isomers, the quantum yields and rate constants of the photolytic reactions were greater for the cis isomers.