Photomediated ring contraction of saturated heterocycles

Shuffling nitrogen with a light push Manipulation of carbon–nitrogen rings is integral to the synthesis of numerous pharmaceutical and agrochemical compounds. Jurczyk et al . report that photoexcitation of carbonyl-substituted cyclic amines can shift the nitrogen from inside to outside the ring framework. The reaction appears to proceed through a 1,5-hydrogen shift to the electronically excited carbonyl, which sets in motion the subsequent carbon–nitrogen and carbon–carbon bonding rearrangements. Several oxygen and sulfur heterocycles were applicable as well. Addition of a chiral phosphoric acid catalyst rendered the reaction asymmetric. —JSY