Visible-Light-Induced Annulative Ring Expansion of Amino- Oxetane/Azetidin/Thietane Derivatives

A visible-light-induced [4 + 2] cycloaddition between N-protected cyclobutanamines containing a heteroatom and olefins is herein reported. The reaction proceeds through a proton-coupled electron transfer (PCET) process to generate a nitrogen-centered radical. Strain-driven ring opening, facilitated by heteroatom conjugation, is followed by the intermolecular olefin addition. This generates the corresponding carbon-centered radical, which is subsequently reduced to an anion before a 6-exo cyclization ensues. This protocol provides diastereoselective access to diverse aminated six-membered heterocycles bearing versatile functional groups.