Iron-Catalyzed Oxidative C(sp3)–C(sp3) Radical Coupling Reaction between Thiohydantoins and O-Acetyloximes for the Synthesis of 1,3-Dibenzyl-3,4-dihydropyrrolo[2,3-d]imidazole-2(1H)-thione Derivatives

Abstract

A unified heteroannelation method to achieve the synthesis of 1,3-dibenzyl-3,4-dihydropyrrolo[2,3-d]imidazole-2(1H)-thione derivatives with an iron catalyst is proposed. The annelation reaction is followed by Csp3-Csp3 radical coupling between thiohydantoins and O-acetyl oximes. The synthetic approach enables access to several alkynylated thiohydantoins and O-acetyl oximes with controlled selectivity for Csp3-Csp3 coupling rather than Csp3-O coupling in moderate to higher yield. The optimization study has been carried out by changing catalyst loading, oxidants, solvents, and varying temperatures. Synthesized compounds were characterized through 1H NMR, 13C NMR, and mass spectral studies.