Iron-Promoted Oxidative Alkylation/Cyclization of Ynones with 4‑Alkyl-1,4-dihydropyridines: Access to 2‑Alkylated Indenones

An iron-promoted oxidative tandem alkylation/cyclization of ynones with 4-alkyl-substituted 1,4-dihydropyridines for the efficient synthesis of 2-alkylated indenones is described. The process occurs via oxidative homolysis of a C–C σ-bond in 1,4-dihydropyridines to generate an alkyl radical followed by the addition of C–C triple bonds in ynones and intramolecular cyclization. A wide range of alkyl radicals could be efficiently transferred to generate a series of synthetically useful 2-alkylated indenones with excellent selectivity under mild conditions.