Visible-Light-Induced Metal-Free Carbonylative Cycloaddition of Acylsilanes with Imines via a Siloxyketene Intermediate

Abstract

Ketenes are highly valuable reactive intermediates in organic synthesis. In particular, the ketene-imine cycloaddition, known as the Staudinger reaction, remains one of the most attractive and widely used methods for the synthesis of β-lactams. Although many methods have been developed for synthesis of ketenes, generating oxy-substituted ketenes via carbonylation of metal carbenes remains challenging due to the lack of suitable carbene precursors. Herein, we report a visible-light-induced in situ generation of siloxyketenes from acylsilanes through a carbon monoxide (CO)-mediated Brook rearrangement. This method enables the carbonylative cycloaddition of acylsilanes with imines under mild and metal-free conditions. The reaction exhibits a broad substrate scope, affording a wide range of valuable α-siloxy-β-lactams in good yields with excellent diastereoselectivity. The synthetic utility of this method has been demonstrated through downstream transformations of the resulting products into useful scaffold motifs. Mechanistic studies and DFT calculation support that the singlet state siloxycarbene species is efficiently captured by CO under photoirradiation, and that nucleophilic attack of the resulting siloxyketene intermediate by the imine is involved in the rate-determining step.

Keywords

Acylsilanes / Brook rearrangement / Ketenes / Carbon monoxide / Visible-light-induced / Metal-free / Cycloaddition / α-Siloxy-β-lactams

RIGHTS & PERMISSIONS

2026 SIOC, CAS, Shanghai, & WILEY-VCH GmbH