An efficient Michael addition of 4-hydroxycoumarins to α,β-unsaturated 2-acyl imidazoles catalyzed by Ni(OTf)2 as a Lewis acid has been developed. A series of 4-hydroxycoumarin derivatives were obtained in excellent yields (up to 96%) with a 2 mol% catalyst loading under mild conditions. Additionally, when a chiral-at-metal rhodium complex was used as the catalyst, moderate enantioselectivity was observed (74% ee).
In this study, we proposed a novel electrochemical dehydrogenative synthetic method for preparing 2-substituted quinoxalines by intermolecular cyclization of aryl alkyl ketones and o-phenylenediamines. This method gave various quinoxalines in yields ranging from 35% to 71%. This novel protocol employs mild reaction conditions and offers moderate to excellent yields, a wide substrate scope, and broad functional-group compatibility. Furthermore, a late-stage functionalization and the wide substrate scope demonstrated the synthetic utility of this protocol.
While enantioselective hydrofluorination methods for activated alkenes represent a notable advance, the resultant enantiomeric excesses remain largely moderate, indicating the necessity for enhancements in precision, efficiency, and scope. We have recently developed an innovative nickel hydride catalytic system that enables regio- and enantioselective C–F bond formation with unactivated alkenes. By utilizing specially designed Bn-BOx ligands for improved selectivity, our approach demonstrates exceptional efficiency and selectivity with β,γ-alkenyl amide substrates. This breakthrough enhances the synthesis of organofluorine compounds, marking a significant advancement in organic synthesis.
1 Introduction
2 Reaction Design of Hydrofluorination
3 Regio- and Enantioselective Hydrofluorination
4 Asymmetric Amplification
5 Conclusions
An electrochemical variant of the alcohol-based oxidative Passerini reaction is reported here. It relies on an indirect anodic oxidation process followed by a three-component coupling, in which TEMPO serves as a key redox mediator. This electrochemical approach permits to operate without the need for a metal catalyst nor oxygen atmosphere and allows the use of nonactivated alcohols as reaction partners. It could be applied to the preparation of good variety of α-acyloxy-carboxamides in yields ranging from 24% to 80%.
Herein, the preparation and characterization of three Ru-based heterogeneous photocatalysts supported on ordered mesoporous silica materials are reported. The photocatalytic activity of these catalysts was evaluated through oxidation, reduction, cycloaddition, and carboxylation reactions and their efficiencies are comparable to the parent [Ru(bpy)3]Cl2 under homogeneous conditions. These photocatalysts are efficiently recovered even after five reaction cycles offering new opportunities in sustainable chemistry.
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