Iron-catalyzed aerobic oxidative amidation of tertiary amines with carboxylic acids

Metal-Free Oxidative Annulation of Phenols and Amines: A General Synthesis of Benzoxazoles

The ubiquity of benzoxazoles in natural products, drugs, and functional materials has stimulated numerous efforts toward their synthesis; however, the developed methods rely on prefunctionalized substrates and lack generality. Under metal-free conditions, a highly general synthesis of benzoxazoles direct from abundant and easily available phenols and amines is developed via a modular phenol functionalization controlled by TEMPO. In the reaction, various phenols and primary amines with a broad range of functional groups are compatible, producing structurally and functionally diverse benzoxazoles (64 examples) without or with trace observation of the byproducts of phenol transformation with amines. The practical synthesis, especially for drug tafamidis, demonstrates decisive advantages in generality, selectivity, efficiency, and atom- and step-economies over traditional methods, even in the cases of low yields. Mechanistically, the radical adducts of TEMPO with ortho-cyclohexa-2,4-dien-1-one radicals rather than the well-recognized cyclohexa-3,5-diene-1,2-diones may serve as intermediates.

Synthesis of 1,2-dihydro-1,3,5-triazine derivatives via Cu(II)-catalyzed C(sp3)-H activation of N,N-dimethylethanolamine with amidines

1,2-Dihydro-1,3,5-triazines and symmetrical 1,3,5-triazines were obtained in up to 81% yields from amidines and N,N-dimethylethanolamine catalyzed by CuCl2. The reaction involves three C-N bond formations during the oxidative annulation process and the mechanism was proposed. This efficient synthesis of 1,2-dihydro-1,3,5-triazines was developed for the first time.

Cu(ii)- or Co(ii)-Catalyzed C(SP3)–H oxidation of N,N-dimethylaminoethanol: facile synthesis of methylene-bridged biindoles and 3-formylindoles selectively

Methylene-bridged biindoles and 3-formylindoles were synthesized with high conversion rate and good regioselectivity using a new carbon donor N,N-dimethylethanolamine, catalyzed by CuCl₂ and CoCl₂ respectively.

Nonclassical Routes for Amide Bond Formation

The present review offers an overview of nonclassical (e.g., with no pre- or in situ activation of a carboxylic acid partner) approaches for the construction of amide bonds. The review aims to comprehensively discuss relevant work, which was mainly done in the field in the last 20 years. Organization of the data follows a subdivision according to substrate classes: catalytic direct formation of amides from carboxylic and amines ( section 2 ); the use of carboxylic acid surrogates ( section 3 ); and the use of amine surrogates ( section 4 ). The ligation strategies (NCL, Staudinger, KAHA, KATs, etc.) that could involve both carboxylic acid and amine surrogates are treated separately in section 5 .

The copper-catalyzed aerobic oxidative amidation of tertiary amines

A general and efficient method for the synthesis of tertiary amides has been developed via the copper-catalyzed aerobic oxidative amidation of tertiary amines.