The Di-p-methane Photorearrangement of 2,3-Disubstituted Benzobarrelenes: the Effect of Substituents of Opposite Polarity on the Regioselectivity

Abstract

The solution phase photochemistry of benzobarrelene derivatives (8) and (11), containing electron-donating and electron-withdrawing substituents, has been studied. The structures of the photoproducts (16)/(20) and (17)/(21) indicate clearly that vinyl-vinyl nitrile (aldehyde) bridging is not operating. The formation of these products is discussed in terms of the stabilizing effect of the substituents on the radical and the destabilizing effect on the formation of the cyclopropane ring.