Modular Synthesis of Densely Functionalized Azetidines: Ni-Catalyzed 1,4-Alkylarylation of 1,3-Enynes with 1-Azabicyclo[1.1.0]butanes through Polar–Radical Relay

An efficient synthesis of densely functionalized azetidines has been achieved via a Ni-catalyzed 1,4-alkylarylation of 1,3-enynes using 1-azabicyclo[1.1.0]butanes (ABBs) and arylboronic acids. This three-component reaction offers an easy way to incorporate an allene fragment into azetidines. The method is characterized by a broad substrate scope and excellent functional group compatibility. Mechanistic studies have revealed a polar-radical relay mechanism for this transformation.