Photoinduced Wolff Rearrangement/Pd-catalyzed [3+2] Cycloaddition Sequence

Ketenes are a kind of important sythons that have been widely used for a variety of[n+2]cycloadditions.Compared with the well-developed ketene cycloadditions through organocatalysis and Lewis acid catalysis,transition metal(TM)catalysis is less utilized in this research area due to the inherent sensitivity of ketene to TM catalysts(i.e.,decarbonylation or polymerization).Thus,exploitation of new reactivity of ketenes through TM catalysis is significant,yet challenging,in the cycloaddition reaction.In this paper,a photoinduced Wollf rearrangement/palladium-catalyzed cycloaddition reaction sequence of a-diazoketones and vinyl cyclopropanes was systematically studied on the basis of our previous work.During this period,we discovered a new reactivity of ketene species.Carbonyl(C=O)instead of carbon-carbon double bond(C=C)participated in the intermolecular cycloaddition reaction.Through the use of P,S ligands developed by our group,highly functional tetrahydrofurans were synthesized with high chemoselectivity after the optimization of reaction conditions and operations.Then,we further investigated the substrate scope of the reaction methodology,and finally achieved a varity of tetrahydrofuran product in 58%-99%yield.The structures of products were confirmed by 1H NMR,13CNMR and mass spectrometry.In addition,according to the previous literatures,we proposed a possible mechanism to understand this reaction.The above research results were published as the first author on Chemical Communications.