Synthesis of Chroman Derivatives by Group Transposition and Atom Swapping in 1‐Tetralones: Single‐Atom Editing Enabled by Oxidative Ring Contraction of Benzoxepine Silyl Ketene Acetals

Abstract Single‐atom editing of complex molecules is steadily filling the chemical toolbox with site‐selective modification reactions. Herein, a stepwise scheme for carbon‐to‐oxygen swap in tetralins leading to privileged chroman scaffolds is presented. Increasing the oxidation state at each stage, the substrate scope naturally extends: starting from tetralins via 1‐tetralones and further via seven‐membered lactones, the transformation results in diverse chroman‐2‐carboxylic acids and chroman‐2‐ols. The efficiency of this synthetic route is governed by the developed new oxidative ring‐contractive transformations of tetrahydrobenzooxepinones, enabled by intermediate silylation into ketene acetals. The described carbon‐to‐oxygen swap is illustrated by 40+ examples, including skeletal editing of natural products and short formal synthesis of Heliannuol E. Formation of chroman‐2‐ols tentatively may proceed via original mechanism with extrusion of carbon monoxide.