A Facile FeCl₃/I₂-Catalyzed Aerobic Oxidative Coupling Reaction: Synthesis of Tetrasubstituted Imidazoles from Amidines and Chalcones

Abstract

A facile and efficient route for the synthesis of tetrasubstituted imidazoles from amidines and chalcones via FeCl3/I2-catalyzed aerobic oxidative coupling has been developed. This new strategy is featured by high regioselectivity and yields, good functional group tolerance, and mild reaction conditions.

Synthesis of 3-Acyl and 2-Acyl Imidazo [1, 2-a]pyridines by I2-Mediated Diamination of α, β-Unsaturated Ketones with 2-Aminopyridines

“…In the case of path a, conjugated addition of ketone 2 with the 2-amino group in 1 results in the intermediate B. Then, the I 2 -mediated cyclization of B via an intramolecular Ortoleva-King reaction [17,9a] , leading eventually to the 2-acyl product (4). The presence of halo groups in substrates 1 favors the path a transformation due to its electron deficiency effect on the pyridine nitrogen.…”

“…Subsequently, Li et al [4] achieved such a transformation with amidines to synthesize tetrasubstituted imidazoles. Recently, Nguyen and Al-Mourabit et al…”

Iron Catalyzed Oxidative Coupling, Addition, and Functionalization

“…At the same time, the oxidative cycloaddition strategy was found to be consistent with amidines as the starting materials to react with electron‐deficient alkenes. In this strategy tetrasubstituted imidazoles were synthesized by the direct oxidative C−H functionalization/cycloaddition by using the iron and iodine catalytic system (Scheme ) . The oxidative cycloaddition reaction is an excellent way to prepare various heterocycles from the readily available reactants.…”

“…ChemCatChem 2016ChemCatChem , 8,2429ChemCatChem -2445 www.chemcatchem.org CÀHf unctionalization/cycloaddition by using the iron and iodine catalytic system (Scheme 39). [30] The oxidative cycloaddition reaction is an excellent way to prepare varioush eterocycles from the readily available reactants. Comparing this protocol to the ones using noblem etal catalyst, the iron and iodine are not only abundant, cheap, and environmentally benign catalysts, but can also offer au seful and widely applicable method in medicinal, organic,and material chemistry.…”

Appel reagent as novel promoter for the synthesis of polysubstituted imidazoles

“…6 The imidazole-containing compounds have also other useful activities such as anthelmintic, 7 antifungal, 8 antiviral activities, 9 antitubercular, 10 antitumor, 11 analgesic, 12 anti-inflammatory, 13 and antibacterial activity. Although the broad variety of synthetic routes have been reported to synthesize imidazole derivatives, 15,16 there are few protocols for preparation of polysubstituted imidazoles. However, some of these methods involve the use of toxic and expensive catalysts or media, and have notable disadvantages such as harsh reaction conditions, long reaction times, and moderate yields.…”