Iron-Catalyzed Convergent Radical Cyclization of Aldehydes with Two Alkenes to 3,4-Dihydropyrans

A novel convergent radical cyclization of an aldehyde with two alkenes has been developed. With this method, polyfunctionalized 3,4-dihydropyrans are built in an efficient and selective manner. The iron-catalyzed redox radical recombinations are proposed for the formation of a 3,4-dihydropyran skeleton.