Visible-Light Photocatalytic and Phosphine-Mediated In Situ Wittig Reaction of Bicyclo[1.1.0]butanes with Aryl Aldehydes

This study reports a new strategy for the in situ Wittig olefination of bicyclo[1.1.0]butanes (BCBs) with aryl aldehydes, enabled by the synergistic combination of blue light photocatalysis and phosphine mediation. This reaction proceeds under mild and efficient conditions, enabling the direct construction of arylidenecyclobutane scaffolds. Mechanistic investigations revealed that the photoinduced phosphine radical effectively activates the highly strained BCB skeleton, triggering ring opening and the in situ formation of a key ylide intermediate, which subsequently undergoes olefination. This method demonstrates good functional group compatibility, offering a new approach to the precise functionalization of strained carbocycles and the modular synthesis of complex alkene architectures.