Synthesis of 1‐azabicyclo[2.1.1]hexanes via formal single electron reduction of azabicyclo[1.1.0]butanes under photochemical conditions

Abstract C(sp 3 )‐rich heterocycles are privileged building blocks for pharmaceuticals and agrochemicals. Therefore, synthetic methods that provide access to novel saturated nitrogen‐containing heterocycles are in high demand. Herein, we report a general synthesis of 1‐azabicyclo[2.1.1]hexanes (1‐aza‐BCH) via a formal cycloaddition of azabicyclo[1.1.0]butanes (ABB) with styrenes under photochemical conditions. To overcome the challenging direct single electron reduction of ABBs, we designed a polar‐radical‐polar relay strategy that leverages a fast acid‐mediated ring‐opening of ABBs to form bromoazetidines, which undergo efficient debrominative radical formation to initiate the cycloaddition reaction. The reaction is applicable to a broad range of ABB‐ketones and we demonstrate the 1‐aza‐BCH products can be further functionalized to access larger saturated, conformationally rigid heterocycles.