Metal-free synthesis of amides by oxidative amidation of aldehydes with amines in PEG/oxidant system

A simple, inexpensive, and efficient one-pot synthesis of amide derivatives were achieved in good to excellent yields via the directly oxidative amidation of aldehydes with amines under PEG/Oxidant system.     

Metal-free one-pot oxidative amination of aldehydes to amides

Metal-free oxidative amination of aromatic aldehydes in the presence of TBHP provides convenient access to amides in 85-99% under mild reaction conditions within 5 h. This method avoids free carboxylic acid intermediates and integrates aldehyde oxidation and amide bond formation, which are usually accomplished separately, into a single operation. Proline-derived amides can be prepared in excellent yields without noticeable racemization.     

Metal-free aerobic oxidative coupling of amines to imines

Oxidative coupling of primary amines to imines is achieved with high to moderate yields by refluxing suspensions of amines and water under one atmosphere dioxygen without any additives. Tandem acid-free aza Diels-Alder reactions for synthesis of N-alkyl-4-pyridones are also accomplished.     

nBu4NI-catalyzed oxidative amidation of aldehydes with tertiary amines

An efficient oxidative coupling protocol for amide formation has been developed. Various tertiary amines and aromatic aldehydes were oxidized to their corresponding tertiary amides in moderate to good yields in the presence of a simple nBu₄NI-catalyst.     

Metal-free synthesis of cyclic di-oxoguanidines via one-pot sequential transformation of amines, carbodiimides and acyl dichlorides

The one-pot sequential reaction of various amines, carbodiimides, and acyl dichlorides has been achieved for the first time under metal-free conditions to provide symmetric cyclic di-oxoguanidines via an unexpected 2,2-dichloro-imidazolidindione intermediate. Acyl dichlorides have a dual function: to serve as the third component and to activate carbodiimides. In sharp contrast, the AlMe(3)-catalyzed sequential reaction from the same substrates gives the isomer.     

Platinum nanowires catalyzed direct amidation with aldehydes and amines

Different from the conventional synthesis methods and substrates, we designed a brand new method for synthesizing amides with platinum nanowires as catalysts and tert-butylhydroperoxide(TBHP) as the oxidant. Influence of factors, such as the catalyst, solvents, and the reaction temperature, were studied to determine the optimal reaction conditions. In addition, we explored the substrate generality and observed excellent yields.     

The first one-pot amidation of alkanes and cycloalkanes

Alkanes (or cycloalkanes) and CO in the presence of superelectrophilic systems CX₄·2AlBr₃ (X = Cl, Br) have been applied for the first time as equivalents of acylium salts in one-pot selective syntheses of amides from amines.     

Mild amidation of aldehydes with amines mediated by lanthanide catalysts

Catalytic amidation of aldehydes with amines is efficiently mediated by homoleptic lanthanide amido complexes, Ln[N(SiMe3)2]3 (Ln = La, Sm, and Y). Amidation reactivity follows the trend: La > Sm approximately Y. These reactions proceed in high yield without added oxidants, bases, and/or heat or light, which are usually required in other catalytic amidation processes. The reaction is demonstrated with a variety of amines, with yields as high as 98% based on amine.     

Pd-catalyzed oxidative amidation of aldehydes with hydrogen peroxide

Using hydrogen peroxide as a key oxidant, catalytic oxidative amidation between aldehydes and amines was effectively carried out with PdCl₂-xantophos as a catalyst in methanol under acidic conditions. The new protocol is mechanistically different from the previous one through β-hydride elimination.     

Visible light photoredox catalysed amidation of carboxylic acids with amines

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.     

Metal-free oxidative cyclization of urea-tethered alkenes with hypervalent iodine

A metal-free oxidative cyclization of ureas onto unactivated alkenes using iodosylbenzene and an acid promoter is described. The products isolated are predominantly bicyclic isoureas resulting from an intramolecular oxyamination reaction. The acid type and urea substitution have a strong effect on the product formed. A variety of substrates form the isourea with high diastereoselectivity via syn addition including di- and trisubstituted alkenes. Hydrolysis of the isourea gives access to new diastereomerically pure prolinol derivatives.     

Synthesis of cytimidine through a one-pot copper-mediated amidation cascade

A concise synthesis of cytimidine was developed utilizing tandem Cu-mediated N-aryl amidations followed by global deprotection. This sequence exploits a regioselective coupling of an iodobenzamide with a halopyrimidine that allows the union of three fragments in a single synthetic manipulation and will permit the efficient and rapid diversification of the cytimidine core.     

Transition-metal-free oxidative amidation of benzyl alcohols with amines catalyzed by NaI: a new method for the synthesis of benzamides

A simple, inexpensive, and efficient method for the synthesis of benzamides via the reaction of benzyl alcohols and amine hydrochloride salts in the presence of NaI as a green catalyst is described. Various derivatives of benzamide were synthesized in moderate to good yields using this method.     

Direct hydrogenation of nitroaromatics and one-pot amidation with carboxylic acids over platinum nanowires

A novel ultrathin platinum nanowire with uniform length and a diameter of 1.5 nm was synthesized by acidic etching of FePt nanowire in methanol. This nanowire was characterized by high‐resolution transmission electron microscopy (HRTEM). X‐ray diffraction (XRD) data indicated that the main plane is (111). The ability of this nanowire to catalyze the heterogeneous hydrogenation of nitroaromatics to give the corresponding amines has been investigated. The catalyst showed satisfactory activity in various solvents under mild conditions and showed excellent stability. The catalytic performance was also evaluated in the one‐pot reduction of nitroaromatics and amidation with carboxylic acids under a hydrogen atmosphere at 100 °C. These methods for the hydrogenation of nitroaromatics and the direct amidation of nitroaromatics with carboxylic acids are simple, economical, and environmentally benign, and have practical advantages for the synthesis of amines and amides without the production of toxic byproducts.     

One-pot oxidative esterification and amidation of aldehydes

During recent years, the direct transformation of aldehydes into esters or amides has developed into a vigorous research area and powerful one-pot oxidative esterification and amidation procedures have been reported. Several concepts that are often complementary in substrate scope, functional group tolerance, and reaction outcome have emerged, thus providing a wide range of alternatives to classical ester and amide synthesis via carboxylic acid intermediates.     

Regioselective one-pot bromination of aromatic amines

[reaction: see text] Treatment of aniline with n-butyllithium and then trimethyltin chloride gave the tin amide (PhNH-SnMe(3)) in situ. Without isolation of the tin amide, reaction with bromine and workup with aqueous fluoride ion gave p-bromoaniline in 76% yield, with no dibromoaniline or o-bromoaniline. Application of this sequence to 11 different aromatic amines gave selective bromination in 36-91% yields, without formation of dibromides. This constitutes a good general method for the regioselective bromination of aromatic amines.     

Metal-free one-pot oxidative conversion of benzylic alcohols and benzylic halides into aromatic amides with molecular iodine in aq ammonia, and hydrogen peroxide

Various primary alcohols, particularly benzylic alcohols, could be converted into the corresponding aromatic amides in good yields in a one-pot manner by treatment with molecular iodine in aq. NH₃, followed by reaction with ∼30% aq H₂O₂. Similarly, various benzylic halides could be also converted into the corresponding aromatic amides in good yields in a one-pot manner by treatment with molecular iodine in aq NH₃, followed by reaction with ∼30% aq H₂O₂. The present reactions involve the metal-free one-pot oxidative conversion of benzylic alcohols and benzylic halides into the corresponding aromatic amides, respectively.     

Highly efficient oxidative amidation of aldehydes with amine hydrochloride salts

A mild and efficient copper-catalyzed oxidative amidation of aldehydes was developed using amine HCl salts and tert-butyl hydroperoxide as an oxidant.     

Platinum nanowires catalyzed direct amidation of aldehydes and amines

Different from the conventional synthesis methods and substrates, we designed a brand new method for synthesizing amides with platinum nanowires as catalysts and tert-butylhydroperoxide(TBHP) as the oxidant. Influence of factors, such as the catalyst, solvents, and the reaction temperature, were studied to determine the optimal reaction conditions. In addition, we explored the substrate generality and observed excellent yields.