Visible‐Light‐Induced Cycloaddition of α‐Ketoacylsilanes with Imines: Facile Access to β‐Lactams

We report the synthesis of β‐lactams from α‐ketoacylsilanes and imines, which proceeds via a formal [2+2] photochemical cycloaddition with in situ generation of siloxyketene. This mild and operationally simple reaction proceeds in an atom‐economic fashion with broad substrate scope, including aldimines, ketimines, hydrazones, and fused nitrogen heterocycles, affording a variety of important β‐lactams with satisfactory diastereoselectivities in most cases. This reaction also features good functional‐group tolerance, facile scalability and product diversification. Experimental and computational studies suggest that α‐ketoacylsilanes can serve as photochemical precursors by engaging in a 1,3 silicon shift to the distal carbonyl group. The synthesis of β‐lactams from α‐ketoacylsilanes and imines is reported, which proceeds via a [2+2] photochemical cycloaddition with in situ generation of siloxyketene. This reaction proceeds in an atom‐economic fashion with broad substrate scope, including aldimines, ketimines, hydrazones, and fused nitrogen heterocycles, and good functional‐group tolerance, affording a variety of β‐lactams with satisfactory diastereoselectivities.