Photoinduced synthesis of functionalized oxetanes via diradical-mediated ring contraction

A versatile photochemical ring contraction is reported for the synthesis of oxetanes under catalyst-free conditions. The reaction is enabled by the use of 2,5-dihydrofurans and diazo compounds under visible light irradiation, delivering functionalized 3-vinyloxetanes as major products. The outstanding features of this protocol include mild reaction conditions, operational simplicity and scalability, as well as excellent functional-group tolerance. DFT calculations indicate that the reaction may proceed through the formation of an oxonium ylide intermediate followed by a diradical-mediated rearrangement and cyclization.