Photodriven Dehydrogenative Homocoupling of Benzylic C–H Bonds Forming Strained C–C Bonds

A photoinduced dehydrogenative homo-coupling reaction of alkylarenes is reported. Gaseous hydrogen is evolved as the sole byproduct and neither oxidants nor hydrogen acceptors are required. The present reaction offers an environmentally benign and atom-economical means for forming sterically strained C–C single bonds. It also gives a remarkable example of photo-driven reactions overcoming a considerable rise in energy.