Pyridine-Boryl Radical-Catalyzed 2π + 2σ Cycloaddition of Bicyclo1.1.0butanes with Alkenes

Bicyclo2.1.1hexanes (BCHs) represent an intriguing class of structurally rigid hydrocarbons that can serve as the bioisosteres of benzenoids in medicinal chemistry. Methods for the synthesis of BCHs are, however, limiting. Reported herein is a facile synthesis of BCHs via a strain-release-driven 2π + 2σ cycloaddition of bicyclo1.1.0butanes (BCBs) with alkenes facilitated by a pyridine-boryl radical catalyst. The mild reaction conditions, broad substrate scope, and decent functional group tolerance of this protocol render it appealing in relevant fields of drug design and synthesis. Theoretical mechanistic studies reveal that a radical relay mechanism is involved. Synthetic applications of the products are performed.