Molecular-oxygen-promoted Cu-catalyzed oxidative direct amidation of nonactivated carboxylic acids with azoles

Catalytic and non-catalytic amidation of carboxylic acid substrates

The present review offers an apt summary of amide bond formation with carboxylic acid substrates by taking advantage of several methods. Carboxamides can be regarded as a substantial part of organic and medicinal chemistry due to their utility in synthesizing peptides, lactams, and more than 25% of familiar drugs. Moreover, they play a leading role in the synthesis of bioactive products with anticancer, antifungal, and antibacterial properties. The data are arranged based on the type and amount of reagents used to conduct amidation and are also divided into the following categories: catalytic amidation of carboxylic acids, non-catalytic amidation, and transamidation.

Synthesis of N-acylbenzimidazoles through [4 + 1] annulation of N-arylpivalimidamides with dioxazolones

Presented herein is a novel and efficient synthesis of N-acylbenzimidazoles through an unprecedented [4 + 1] annulation of N-arylpivalimidamides with dioxazolones.

Cu(i) catalysed annulation of isothiocyanates/isocyanates with 2-iodo-sulfonamides: synthesis of benzodithiazines, benzothiadiazinones, benzothiazinylidene-anilines and benzothiazolylidene-anilines

An efficient Cu(i)-catalysed cyclisation reaction of 2-iodobenzene sulfonamides with aryl-isothiocyanates and isocyanates that affords functionalised benzodithiazines and benzothiadiazinones, respectively, has been developed. Thus, in the reaction with aryl isothiocyanates (Ar-N[double bond, length as m-dash]C[double bond, length as m-dash]S), the C[double bond, length as m-dash]S moiety participates in the cyclisation leading to a dithiazine. By contrast, in the case of aryl isocyanates (Ar-N[double bond, length as m-dash]C[double bond, length as m-dash]O), the N[double bond, length as m-dash]C part is involved in the cyclisation and a thiadiazinone is obtained. Analogous reactions of isothiocyanates with N-tosyl-2-iodo-anilines and 2-iodo-benzyl sulfonamides afford (benzothiazin-2-ylidene)anilines and (benzothiazol-2-ylidene)anilines, respectively. Probable mechanistic pathways are briefly discussed.

Chemoselective acylation of benzimidazoles with phenylacetic acids under different Cu catalysts to give fused five-membered N-heterocycles or tertiary amides

C-N bond formation via a copper-catalyzed aerobic oxidative decarboxylative tandem protocol was realized. The phenylacetic acids which contain ortho-X (X = F or Br) on the aromatic ring will render a fused five-membered heterocycle via a tandem aromatic nucleophilic substitution and aerobic oxidative decarboxylative acylation at the C(sp(2))-H bond of benzimidazoles under the Cu(OAc)2/K2CO3/BF3·Et2O catalytic system, while with CuBr as the catalyst and pyridine as the base, N-acylation occurred and tertiary amides were obtained.