Photochemical Cascade Nitrile Activation via a Carbene-Nitrene Relay

The deliberate integration of reactive intermediates into programmed bond-forming sequences represents a powerful approach for advancing organic synthesis and enabling novel transformations. Among these intermediates, transient nitrene species are particularly attractive due to their capacity to generate two new X─N covalent bonds. However, the development of nitrene-mediated reactions has been hindered by difficulties in controlling their high reactivity and the limited availability of efficient precursors. We hypothesized that a catalytic strategy enabling the sequential generation of carbene and nitrene intermediates could facilitate the cascade activation of common nitriles, thereby unveiling their latent potential as nitrene sources. In this work, we report a methodology for the catalytic generation of a sulfoxonium (S^VI)-substituted metal-carbenoid, which undergoes reaction with nitriles to afford S^VI-azirine species. Under photochemical and metal-mediated activation conditions, these three-membered strained rings rearrange to form vinyl metal-nitrenoid intermediates. Subsequent B-H insertion of the nitrenoid with boranes delivers tetra-substituted enamine products. The described approach proceeds with high efficiency and selectivity, traverses two highly reactive intermediates, and establishes an unprecedented activation mechanism for conventional nitrile substrates.