Energy Transfer-Enabled Diradical Carbonylative Cyclization of Bicyclo[1.1.0]butanes with CO and Alkenes/Alkynes

Radical carbonylation has emerged as a crucial and alternative method for introducing carbonyl groups with enhanced selectivity and broader substrate compatibility. However, currently, the substrates suitable for these processes are primarily limited to those that can undergo radical induction to form the corresponding monoradicals as key intermediates. Herein, we report a photocatalytic energy transfer-enabled diradical carbonylative cyclization of bicyclo[1.1.0]butanes with CO and commercially abundant alkenes/alkynes to assemble a variety of 4-oxo bicyclo[3.1.1]-heptanes and heptenes. The subsequent diversification of the incorporated carbonyl group further allows rapid exploration of structurally varied derivatives. Density functional theory computations reveal that the success of the reaction is determined by the competition between the desired three-component [2σ + 2 n + 2π] cyclization pathway and the [2σ + 2π] cycloaddition and alkene dimerization pathways.