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(CF3)ppy](2)(dtbpy))PF6 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.

Automated summary

2-Cyanochromone (1) undergoes visible light-induced photocycloadditions with various alkenes using (Ir[dF(CF3)ppy](2)(dtbpy))PF6 as the photosensitizer. Mono-, di-, and trisubstituted styrenes and acrylonitriles produce [2 + 2] cycloadducts with excellent regiocontrol and high diastereoselectivity. Trialkyl-substituted alkenes yield cyclopentenone-fused chromones through a [3 + 2] cycloaddition process in moderate yields.