Ring Expansions of 1,2-Amino Alcohols to Amine Heterocycles Enabled by Proton-Coupled Electron Transfer

Biologically active molecules are often composed of ring structures that precisely position functional groups to enable target-specific interactions. The iterative permutation of these structural arrangements is central to the modern drug discovery process, necessitating de novo synthesis to access isomeric compounds with distinct biological properties. However, methods to interconvert saturated ring systems remain limited. Here we report a general method for the peripheral-to-core nitrogen internalization of amino cycloalkanols to access N-heterocycles of various oxidation states. In this process, an excited-state iridium chromophore and weak Brønsted base cooperatively promote the endergonic redox isomerization of cyclic amino alcohols to linear amine-containing products that undergo in situ cyclization. This strategy enables the expansion, contraction, and carbon-to-nitrogen substitution of cyclic amino alcohols, providing access to structurally distinct heterocyclic scaffolds.