6522
J. Am. Chem. SOC.1981,103, 6522-6524
Scheme I
bornene. It is inherent in this mechanism that (as observed) neither the a nor the b products are formed in the presence of the triplet quencher, 02,or in the absence of ketone. The 2% of epoxide formed in experiment 3 of Table I suggests incomplete degassing, and also that excited acetone which escapes quenching can sensitize a little epoxidation in competition with the processes of Scheme I. The following 13CNMR spectra are definitive for identification of the key products: 1, 151.45, 50.16, 42.75, 25.21; 2, 153.86,
+ c H3
I*
c
CH +
