Iron-Catalyzed Oxidative C(sp3)–C(sp3) Radical Coupling Reaction between Thiohydantoins and O-Acetyloximes for the Synthesis of 1,3-Dibenzyl-3,4-dihydropyrrolo2,3-dimidazole-2(1H)-thione Derivatives

Abstract A unified heteroannelation method to achieve the synthesis of 1,3-dibenzyl-3,4-dihydropyrrolo2,3-dimidazole-2(1H)-thione derivatives with an iron catalyst is proposed. The annelation reaction follows a C(sp3)–C(sp3) radical coupling between a thiohydantoin and an O-acetyloxime. The synthetic approach enables access to several alkynylated thiohydantoins and O-acetyloximes with controlled selectivity toward C(sp3)–C(sp3) coupling rather than C(sp3)–C(sp3)–O coupling in moderate to high yields. An optimization study has been carried out by changing the catalyst loading, oxidants, solvents, and temperature. Synthesized compounds were characterized through 1H and 13C NMR and mass spectral studies.