Application of Conjugated Carbonyls in the Synthesis of Heterocycles via Oxidative Cycloaddition and Cyclization Reactions

Dibromomethane-Triggered Electrochemical Cyclization of Enaminones with Amidines for the Synthesis of 5-Acylimidazoles

An electrochemical tandem cyclization of enaminones with amidines has been reported for the first time using dibromomethane as an initiating agent in an undivided cell. Following this protocol, a vast variety of polysubstituted 5-acylimidazoles were obtained in moderate to good yields without the use of external oxidants. Mechanistic studies indicate that the bromide anion, electroreductively generated from dibromomethane, acts as a redox mediator to complete the catalytic cycle.

Synthesis of fully functionalized spirostanic 1,2,3-triazoles by the three component reaction of diosgenin azides with acetophenones and aryl aldehydes and their biological evaluation as antiproliferative agents

Diosgenin is of significant interest due to its biological activity and synthetic application. In this study, we report the synthesis of a series of spirostanic 1,4,5-trisubstituted 1,2,3-triazoles by the three component reaction of (25R)-6-azidospirostan-3,5-diols with acetophenones and aryl aldehydes. The one-pot two step synthesis proceeds through the in situ formation of (E)-chalcones and copper catalyzed reaction with organic azides in DMF medium. Structural diversity was achieved by varying the aldehyde and acetophenone nature as well as the spirostanic azide stereochemistry. The results of in vitro biological assays showed that fully decorated spirostanic 1,2,3-triazoles exerted significant and selective antiproliferative activity against MCF-7, glioblastoma (SNB-19, T98G, A-172) and neuroblastoma (IMR-32, SH-SYSY) (HCT116) cell lines (GI₅₀ in the single-digit micromolar range). The data revealed that benzoyl and aryl substitutions in the triazole ring introduced at the 6β-position significantly improved the anti-tumor activity of (25R)-6-azidospirostan-3β,5α-diols. This position on the spirostan core may be the favourable to synthesize of potent anticancer leads from diosgenin.

Synthesis of Fully Substituted 5-(o-Hydroxybenzoyl)imidazoles via Iodine-Promoted Domino Reaction of Aurones with Amidines

An iodine-promoted domino reaction of aurones with amidines has been successfully explored. The reaction proceeds in a consecutive manner containing Michael addition, iodination, cyclization from intramolecular nucleophilic substitution, and dehydrogenative aromatization from spiro ring opening. Following this novel strategy, a variety of 1,2,4-trisubstituted 5-(o-hydroxybenzoyl)imidazoles were efficiently synthesized in moderate to good yields from readily available starting materials. A plausible mechanism has been proposed.

Recent Advances in the Transition Metal-Free Synthesis of Heterocycles from α, β-Unsaturated Ketones

Heterocyclic compounds are an inevitable part of our life. These important classes of molecules have a wide range of applications starting from life-sustaining drugs to agrochemicals. Numerous methods, including metal...