Iron-Catalyzed Divergent Tandem Radical Annulation of Aldehydes with Olefins toward Indolines and Dihydropyrans

Iron-catalyzed divergent tandem radical annulations of aldehydes with olefins are reported. The new strategy allows the rapid and efficient construction of various multifunctionlized indolines (R = Ar) and dihydropyrans (R = Me), which are significant skeletons in bioactive natural products and pharmaceuticals. The substituents of tertiary amines play vital roles to facilitate the desired transformation. Mechanistic studies on indoline formation disclose that the homolytic cleavage of the carbonyl C–H bond might be involved in the rate-determining step, while dissociation of the aromatic C–H bond was most likely included in the product-determining step.