Highly peri- and stereoselective intramolecular photocycloaddition and cyclisation of N-(1-naphthylethyl)prop-2-enamides

Abstract

Control of three modes of intramolecular reactions, [2+2] and [4+2] cycloadditions, and Type-II cyclisation, is attempted in the photochemical reaction of N-(naphthylethyl)prop-2-enamides. The reactions are affected by the enamide substituents and the sensitisation conditions used. Acryloyl derivatives undergo [2+2] cycloaddition and Type-II cyclisation. The two reactions occur selectively depending on the sensitiser used, benzophenone sensitisation affording the [2+2] cycloadducts whereas the Type-II cyclisation products are obtained exclusively by benzene sensitisation. In contrast, photolysis of cinnamoyl derivatives results in the formation of [4+2] cycloadducts.