Direct lactonization from 1,3-dienes and malonate esters mediated by a combination of iodine and visible light

This manuscript describes the reaction of dienes with carbonyls in the presence of molecular iodine under visible light irradiation to furnish the corresponding butyrolactones with complete site selectivity. The reaction proceeds via site selective sequential addition of iodine radical, which is generated from molecular iodine under visible light irradiation, to dienes to form a reactive intermediate, followed by substitution and cyclization. A variety of dienes and carbonyls are well tolerated under the reaction conditions. This transformation constitutes the first iodine radical-mediated intermolecular lactonization reaction of dienes. (C) 2019 Elsevier Ltd. All rights reserved.