Iodine-mediated Z-selective oxidation of ketones to α,β-unsaturated esters: synthesis and mechanistic studies

The Z-selective oxidation of simple acyclic ketones to Z-2,3-trisubstituted α,β-unsaturated esters is described. Enolates generated under the reaction conditions undergo double iodination followed by a Favorskii-related rearrangement to the unsaturated ester. This reaction represents the first stereoselective one-step transformation of ketones to α,β-unsaturated esters. Mechanistic studies suggest that an electrocyclic reaction governs the Favorskii-related rearrangement.