EDA-complex photoactivation of thianthrene-based radical precursors enables divergent access to functionalized saturated heterocycles

Abstract

We report a novel EDA complex stabilized by π-π and CH-π interactions between thianthrene-derived radical precursors and unsaturated carboxylic acids or alcohols. This photocatalyst-free strategy allows access to different disubstituted heterocycles. This transformation proceeds efficiently under visible-light irradiation, delivering a broad array of structurally diverse lactones and tetrahydrofuranes in good to excellent yields. Both aryl and alkyl-derived thianthrenium salts are competent substrates, including primary, secondary, and sterically hindered tertiary alkyl derivatives. In addition, this work shows the first example of iminothianthrenes participating in EDA-complex driven photochemistry providing access to aminated tetrahydrofuranes. UV-Vis spectroscopy, NMR analysis and DFT calculations support the formation of the groundstate EDA complex stabilized by π-π and CH-π interactions. The reaction proceeds via a non-chain pathway as indicated by the photochemical quantum yield.