Cobalt-catalyzed C–H activation by means of oxazolinyl assistance set the stage for versatile direct amidations with ample substrate scope. Thus, a high-valent cobalt(III) catalyst enabled C–H ...amidations with excellent levels of positional and chemo-selectivities. Mechanistic studies provided strong support for a kinetically relevant C–H functionalization.
The Co(III)-catalyzed direct C–H amidation of arenes has been developed using O-acylcarbamates as a convenient amino source. This reaction proceeded in high efficiency under external oxidant-free ...conditions with a broad range of arene substrates, including 6-arylpurines bearing sensitive functional groups, thus furnishing synthetically versatile arene N-carbamate products.
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•No coupling reagent.•Moisture tolerance.•Highly selectivity.•Mild reaction condition.•Application in peptide.
A visible-light promoted photoredox catalysed, green one-pot approach ...for the amidation of carboxylic acids with amines has been developed for the synthesis of diverse aliphatic and aromatic amides. The proposed strategy is extendable also to biologically active amides and could represent a low-cost alternative to the common synthetic pathways. The developed strategy may hold great potential for a comprehensive display of biologically interesting peptide synthesis and amino acid modification.
A rhodium-catalyzed direct and regioselective amidation of the cage B(4)–H bond in a wide range of o-carboranes with alkyl-, aryl-, and heteroaryl-substituted dioxazolones is demonstrated by ...carboxylic acid-assisted B(4)–H bond activation in carborane clusters, providing a number of amidated o-carboranes in high yields with the release of carbon dioxide. Moreover, the selective 2-fold decarboxylative amidation reaction of the cage B(4)–H bond in o-carborane was accessed.
α-Ketoamides and their derivatives are key constituents of natural products, biologically relevant molecules, drug and drug candidates, and functional materials. Further, they are versatile and ...valuable intermediates and synthons in a number of functional group transformations and total syntheses. In recent years tremendous growth has been realized in the development of synthetic methods for α-ketoamide preparation and their applications in synthetic and medicinal chemistry. Among the various catalytic methods of α-ketoamide formation, two approaches, namely double aminocarbonylation and oxidative amidation, have received much more attention and have been greatly studied because of the ready availability of the starting materials, use of carbon monoxide (CO) as a direct source of carbonyl functionalities, and use of molecular oxygen (O2) or air as a green terminal oxidant and/or reactants. Catalyzed α-ketoamide formation can be roughly classified into metal- and nonmetal-catalyzed processes. In the context of metal catalysis, most reactions involving metals are performed using palladium (Pd) and copper (Cu); however, other metals such as gold (Au), silver (Ag), and iron (Fe) based catalysts have also been investigated to some extent. On the other hand, nonmetal-catalyzed α-ketoamide syntheses are mainly restricted to iodine-based catalysts in the presence or absence of other promoters. Our objective in this review is to highlight the important research endeavors related to catalytic α-ketoamide synthesis, which include the trends in the catalytic synthesis of α-ketoamides, new breakthroughs, and recent advances up to March 2016.
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A convenient protocol for amide bond formation for electron deficient amines and carboxylic acids is described. Amide coupling of aniline derivatives has been investigated with a ...number of reagents under a variety of reaction conditions. The use of 1 equivalent of EDC and 1 equivalent of DMAP, catalytic amount of HOBt and DIPEA provided the best results. This method is applicable for the synthesis of a range of functionalized amide derivatives with electron deficient and unreactive amines.
A catalytic system is discovered for the intramolecular C–H amidation of N-phenoxy acetamide derivatives. Herein, a cobalt catalyst has been employed for the olefin-mediated ortho C–H ...functionalization. Moreover, a monocyclic olefin, maleimide, has been used as a transient mediator instead of well-established bicyclic norbornenes. Maleimide promotes a Co(III) intermediate to undergo oxidative addition into the O–N bond to form a Co(V) nitrene species and subsequently directs nitrene addition to the ortho position. Mechanistic study and density functional theory (DFT) study support the proposed mechanism. The products derived from this methodology have been demonstrated as a ligand in the C–H olefination reaction. Furthermore, the synthetic utility of this methodology was demonstrated via the ortho-amidation of estrone.
The synthesis of amides is of huge importance in a wide variety of industrial and academic fields and is of particular significance in the synthesis of pharmaceuticals. Many of the well established ...methods for amide synthesis involve reagents that are difficult to handle and lead to the generation of large quantities of waste products. As a consequence, there has been a considerable amount of interest in the development of new approaches to amide synthesis. Over the past few years a wide range of new reagents and catalysts for direct amidation of carboxylic acids have been reported. In addition, the interconversion of amide derivatives through transamidation is emerging as a potential alternative strategy for accessing certain amides. This microreview covers recent developments in the direct amidation of carboxylic acids and the interconversion of amides through transamidation. The advantages and disadvantages of the various methods are discussed, as well as the possible mechanisms of the reactions.
Amide formation is one of the most important processes in synthetic chemistry, particularly for pharmaceutical synthesis. Nevertheless, many existing methods are inefficient and produce large quantities of waste products. Considerable effort has thus been devoted to the development of new approaches; here we review recently reported methods for direct amidation of carboxylic acids and for transamidation.
The present study reports the successful synthesis of two important and abundant functional groups "ester and amide" by N,N′-diisopropylcarbodiimide (DIC) in water as a green solvent. A wide range of ...substrates could be employed with high functional group tolerance. The products were obtained in high yields after short reaction times. This method provides an efficient, economic, simple and very mild protocol for ester and amide bond formation in aqueous media. In addition, this work not only may lead to environmentally benign systems but also will provide a new aspect of organic chemistry in water.
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