NHC-Mediated Olefin Amidoacylation via Amidyl Radical Intermediates Leading to 5- and 6-Membered Keto-Lactams

Abstract

N-Heterocyclic carbene (NHC) catalysis has emerged as a versatile organocatalytic platform for radical-mediated acyl transfer into readily available molecular frameworks. However, its engagement with N-centered radicals remains underexplored. Herein, we report a diastereoselective (up to >19:1 dr) access to 5- and 6-membered keto-lactams via NHC-mediated amidoacylation of olefin-tethered dioxazolones with aldehydes under transition metal-free and photocatalyst-free conditions. It is proposed that proton-coupled electron transfer (PCET) from NHC-derived Breslow intermediate to dioxazolones may furnish amidyl radicals to undergo 5-exo- or 6-endo-trig cyclization, followed by radical–radical coupling with an in-situ-generated persistent ketyl radical.