Visible light-induced iridium(III)-sensitized [2 + 2] and [3 + 2] photocycloadditions of 2-cyanochromone with alkenes.

2-Cyanochromone (1) readily undergoes visible light-induced photocycloadditions with diverse alkene partners mediated by (Ir[dF(CF 3 )ppy] 2 (dtbpy))PF 6 as the photosensitizer. While mono-, di- and trisubstituted styrenes and acrylonitriles as the reactants lead to [2 + 2] cycloadducts with good regiocontrol and high diastereoselectivity, the use of trialkyl-substituted alkenes allows for the isolation of cyclopentenone-fused chromones resulting from a [3 + 2] cycloaddition process in moderate yields.