Decarboxylative/Oxidative Amidation of Aryl α-Ketocarboxylic Acids with Nitroarenes and Nitroso Compounds in Aqueous Medium

[(NHC)Pd(OAc)2]: Highly Active Carboxylate Pd(II)-NHC (NHC = N-Heterocyclic Carbene) Precatalysts for Suzuki-Miyaura and Buchwald-Hartwig Cross-Coupling of Amides by N-C(O) Activation

In the past eight years, the selective cross-coupling of amides by N-C(O) bond activation has emerged as a highly attractive manifold for the manipulation of traditionally unreactive amide bonds. In this Special Issue on Next-Generation Cross-Coupling Chemistry, we report the Suzuki-Miyaura and Buchwald-Hartwig cross-coupling of amides by selective N-C(O) cleavage catalyzed by bench-stable, well-defined carboxylate Pd(II)-NHC (NHC = N-heterocyclic carbene) catalysts {[(NHC)Pd(O2CR)2]}. This class of Pd(II)-NHCs promotes cross-coupling under exceedingly mild room-temperature conditions owing to the facile dissociation of the carboxylate ligands to form the active complex. These readily accessible Pd(II)-NHC precatalysts show excellent functional group tolerance and are compatible with a broad range of amide activating groups. Considering the mild conditions for the cross-coupling and the facile access to carboxylate Pd(II)-NHC complexes, we anticipate that this class of bench-stable complexes will find wide application in the activation of amide N-C(O) and related acyl X-C(O) bonds.

Sulfur-Mediated Decarboxylative Amidation of Cinnamic Acids via C═C Bond Cleavage

A new strategy for the synthesis of amides has been developed using sulfur-mediated decarboxylative coupling of cinnamic acids with amines via oxidative cleavage of the C═C bond.

Direct Synthesis of α-Ketoamides via Copper-Catalyzed Reductive Amidation of Nitroarenes with α-Oxocarboxylic Acids

Nitroarenes are known for their stability, low toxicity, easy availability, and cost-effectiveness, making them one of the most fundamental chemical feedstocks. The direct utilization of nitroarenes as nitrogen sources in amidation reactions offers significant advantages over using arylamines. Herein, we disclose a streamlined method for constructing α-ketoamides through the direct coupling of nitroarenes with α-oxocarboxylic acids. This transformation obviates the need for preparing, isolating, and purifying arylamines, leading to improved efficiency, cost-effectiveness, and time savings.

Reductive cross-coupling of N-acyl pyrazole and nitroarene using tetrahydroxydiboron: synthesis of secondary amides

We report on a new method for the synthesis of amides using acyl pyrazoles and nitroarenes under reducing conditions. It was found that acyl pyrazoles react with organo-nitro compounds in the presence of B2(OH)4, giving the corresponding amides in good yields. We demonstrated that benzoyl pyrazoles having various substituents and nitroarenes with different substituents can be used to produce a range of N-substituted benzamides. The method shows good functional group tolerance and has potential application in the synthesis of a variety of organic molecules.

Nickel-Catalyzed Reductive Cross-Coupling of N-Acyl and N-Sulfonyl Benzotriazoles with Diverse Nitro Compounds: Rapid Access to Amides and Sulfonamides

Herein we report a Ni-catalyzed reductive transamidation of conveniently available N-acyl benzotriazoles with alkyl, alkenyl, and aryl nitro compounds, which afforded various amides with good yields and a broad substrate scope. The same catalytic reaction conditions were also applicable for N-sulfonyl benzotriazoles, which could undergo smooth reductive coupling with nitroarenes and nitroalkanes to afford the corresponding sulfonamides.

Direct Access to Amides from Nitro-Compounds via Aminocarbonylation and Amidation Reactions: A Minireview

The ubiquity of the amide bond in functional molecules including proteins, natural products, pharmaceuticals, agrochemicals and materials provides impetus to design and develop newer strategies for the generation of this linkage. Owing to growing awareness about sustainability and development of benign strategies, the traditional route of synthesis of amides via reaction between carboxylic acids and amines in the presence of stoichiometric amount of coupling reagents is tagged to be harsh and wasteful. In one of the unconventional routes, nitro compounds are used directly as amine surrogates for preparing amides mostly via aminocarbonylation and amidation reactions. Typically, such processes involves nitroarenes owing to their propensity to transform into nitroso, hydroxylamine, diazo, hydrazine or aniline intermediates in situ under the influence of suitable catalyst or oxidant. This short review provides the comprehensive overview of these reactions including insight into the scope and their mechanisms.