A high yield method for the direct amidation of long-chain fatty acids

The amidation of long-chain fatty acids is the key step for preparing surfactants with excellent interfacial activity. Gas chromatography–mass spectrometry was employed to detect the reactants and products in the direct amidation reactions. The conversion and the concentration of the amides in the reaction process were also investigated to determine the best catalyst, the reaction rate constants, and activation energy. It was identified that the amidation reaction of the long-chain phenyl fatty acid was a zero-order reaction and 3,4,5-trifluorophenylboronic acid was the most effective catalyst by which the activation energy reduced to 55.79 kJ/mol from 95.44 kJ/mol. The method can be applied to other long-chain fatty acids, saturated or unsatureated. The turning-over-temperature was 156°C, over which high yields can be achieved without any catalyst. These provide a reference for the preparation of long-chain fatty acid amides.     

Fabrication of polyurethane binders grafted with functional reactive plasticizers by a catalyst-free click reaction

The design of nonmigratory energetic plasticizers with low sensitivity and high performance is of great significance but challenging. Herein, two nonmigratory norbornane-based reactive plasticizers (NRPs) are attached covalently to poly(glycidyl azide-co-tetrahydrofuran) (PGT)-based polyurethanes (PUs), offering a reliable, self-stable, and alternative energy source originating from ring strain, while mitigating the dangers to the environment by preventing migration. A binary mixture of PGT and NRPs is thermodynamically miscible up to 50/50 w/w. The catalyst-free click reactivity of the NRPs toward PGT evaluated by the activation energy is verified by calculating the frontier molecular orbital energy levels. The absent weight loss of the pure NRPs evident from the measured thermal stability of the NRP/PGT-based PU binders indicated that the NRPs react completely with the PGT matrix. The tensile properties of the PGT-based PU binder by the inclusion of NRPs increased with increasing NRP content because of the increased number of triazole groups and the norbornane moiety. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 402–411     

Dibenzothiophenesulfilimines: A Convenient Approach to Intermolecular Rhodium-Catalysed C−H Amidation

A sulfilimine-based Group 9 transition-metal-catalysed C−H amidation procedure is reported. Dibenzothiophene-based sulfilimines were shown to constitute a class of novel amidation reagents which enable the transfer of a wide range of N-sulfonyl and N-acyl moieties. It was demonstrated that sulfilimines, which are easily accessible from cheap reagents, are safe-to-handle and represent broadly applicable amidation reagents. The dibenzothiophene can be recycled after use. The C−H amidation was shown to proceed with high selectivity and gave the mono-amidated products, mostly in good to excellent yields.     

Synthesis of β‐Keto Sulfones by a Catalyst‐Free Reaction of Aryldiazonium Tetrafluoroborates,Sulfur Dioxide,and Silyl Enol Ethers

A green approach for the generation of β‐keto sulfones through a reaction of aryldiazonium tetrafluoroborates and sulfur dioxide with silyl enol ether under catalyst‐ and additive‐free conditions has been realized. This reaction proceeds efficiently at room temperature and goes to completion in half an hour. During the reaction process, aryldiazonium tetrafluoroborate is treated with DABCO ⋅ (SO₂)₂ (DABCO=1,4‐diazabicyclo[2.2.2]octane) to provide a sulfonyl radical as the key intermediate, which then initiates the transformation. Oxidants or metal catalysts are avoided, and the presence of DABCO also plays an important role in the reaction.     

Propargyl‐Assisted Selective Amidation Applied in C‐terminal Glycine Peptide Conjugation

Alkyl esters, such as propargyl esters, typically lack the electron‐withdrawing inductive effects needed to participate in nucleophilic acyl substitution reactions. Herein, we report an unusual observation in which glycine propargyl ester derivatives displayed selective, base‐independent reactivity towards linear alkylamines under mild, metal‐free conditions. Through global reaction route mapping (GRRM) modeling calculations, it is predicted that these observations may be governed by factors related to hydrogen‐bonding and intermolecular interactions, rather than electron‐withdrawing inductive effects. Based on this concept of propargyl‐assisted selective amidation, a direct application was made to develop a novel site‐specific C‐terminal glycine peptide bioconjugation technique as a proof‐of‐concept, which relies upon the selective reactivity of glycine propargyl esters over that of aspartate and glutamate side‐chain‐linked propargyl esters.     

Catalyst-free and solvent-free synthesis of novel symmetrical bisthioglycolic acid derivatives

A simple, efficient, eco-friendly, and cost-effective method has been developed for the synthesis of symmetrical bisthioglycolic acid derivatives by a one-pot reaction of aldehydes or ketones with thioglycolic acid under solvent- and catalyst-free conditions in excellent yields (87–97%). The advantages of this novel protocol include the excellent yields, operational simplicity, short reaction times, and the avoidance of the use of organic solvents and catalysts.     

Oxidative Coupling of o-Phenylenediamine with Arylmethylamines to Synthesize Aryl-Substituted Benzimidazoles Under Catalyst-Free and Solvent-Free Conditions

Solvent-free oxidative synthesis of benzimidazoles from arylmethylamines and o-phenylenediamine has been achieved under catalyst-free conditions. This reaction can use tert-butyl hydroperoxide (TBHP) as the oxidant, and a wide variety of derivatives were obtained in good yields. The reaction mechanism was proposed and this method provides a direct and practical approach for the preparation of substituted benzimidazoles.     

Highly substituted indol-2-ones, quinoxalin-2-ones and benzodiazepin-2,5-diones via a new Ugi(4CR)-Pd assisted N-aryl amidation strategy

A new strategy employing an Ugi four-component reaction and a palladium-assisted intramolecular N-aryl amidation reaction is reported. The straight forward two-step synthesis generates N-heterocyclic compounds with four points of diversity from trivial starting materials with acceptable yields. This new reaction is also suitable for the generation of compound libraries.     

4-Hydroxy-2-quinolones. 111. Simple synthesis of 1-substituted 4-methyl-2-oxo-1,2-dihydroquinoline-3-carboxylic acids

A preparative method of obtaining 1-substituted 4-methyl-2-oxo-1,2-dihydroquinoline-3-carboxylic acids is proposed. Features of their spatial structure have been studied. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 69–74, January, 2007.     

Simple synthesis of a terpenophenol—chlorin conjugate with an amide bond

A terpenophenol with a butylaminomethyl group was synthesized and conjugated to a chlorin macrocycle through formation of an amide bond without using activating reagents. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 561–563, November–December, 2007.