Organophotocatalytic [2+2] cycloaddition of electron-deficient styrenes

A visible light organophotocatalytic [2+2] cycloaddition of electron-deficient styrenes is described. Photocatalytic [2+2] cycloadditions are typically performed with electron-rich styrene derivatives or α,β-unsaturated alkenes, and with transition-metal-based catalysts. We have discovered that an organic cyanoarene photocatalyst is able to deliver high-value cyclobutane products bearing electron-deficient aryl substituents in good yields. A range of electron-deficient substituents are tolerated and both homodimerizations and intramolecular [2+2] cycloadditions to fused bicyclic systems are available using this methodology.