A vinylogous Norrish reaction as a strategy for light-mediated ring expansion

Abstract

The reactions of bicyclic divinyl ketones display wavelength-dependent changes in product formation. UV irradiation results in the formation of competitive and tricyclic unsaturated ketones that subsequently undergo ring expansion and reaction with a range of nucleophiles. DFT calculations and transient absorption experiments were completed that are consistent with a vinylogous Type II Norrish pathway.