Synthesis of quinazolinones from o-aminobenzamides and benzyl amines under metal-free conditions

A convenient and transition-metal free protocol for quinazolinones synthesis with o-aminobenzamides and benzyl amines as substrates has been developed. Using H₂O₂ as the oxidant, various quinazolinones were obtained in moderate to good yields under metal-and additive-free conditions.     

Intramolecular oxidative diamination and aminohydroxylation of olefins under metal-free conditions

A metal-free procedure that is simple to operate and convenient to handle was developed for the facile intramolecular oxidative diamination of olefins using an iodobenzene diacetate oxidant and a halide additive to furnish bisindolines at room temperature. The present reaction is featured by mild conditions, a broad substrate scope, and excellent functional group tolerance. The same protocol was successfully extended to the aminohydroxylation.     

Hypervalent iodine mediated C-H amination of quinoxalinones with heteroaromatic amines under metal-free conditions

An efficient and facile method for C–H amination of quinoxalinones with heteroaromatic amines under metal-free conditions has been described. In the presence of hypervalent PIDA reagent, the desired products with various groups were obtained with moderate to high yields.     

Direct and mild palladium-catalyzed aerobic oxidative synthesis of imines from alcohols and amines under ambient conditions

By ligand, TEMPO, and base screening, we developed a mild and green one-pot imine synthesis from alcohols and amines via a low-loading palladium-catalyzed tandem aerobic alcohol oxidation-dehydrative condensation reaction that can be readily carried out in open air at room temperature.     

Convenient metal-free direct oxidative amidation of aldehyde using dibromoisocyanuric acid under mild conditions

A facile method for the direct synthesis of amides from aldehydes is described. Amide bonds were synthesized by an oxidative amidation in the presence of dibromoisocyanuric acid (DBI). Treatment of aromatic and aliphatic aldehydes with dibromoisocyanuric acid generated acyl bromide intermediates, which were employed to react with a variety of secondary and primary amines to give amides. Through this reaction method, various amides were synthesized directly from aldehydes under mild conditions in high yields and short times. This facile and efficient procedure provides potential strategy for the direct synthesis of amides from aldehydes.     

NH4I-promoted N-acylation of amines via the transamidation of DMF and DMA under metal-free conditions

An unprecedented NH₄I-promoted N-formylation and N-acetylization of various amines with dimethylformamide (DMF) and dimethylacetamide (DMA) has been developed. This protocol shows broad substrate scope for aromatic, aliphatic, and heterocyclic amines, which provides a metal-free strategy for N-acylation featuring mild reaction conditions, as well as inexpensive and readily available starting materials.     

Direct hydrogenation of amides to alcohols and amines under mild conditions

The selective, direct hydrogenation of amides to the corresponding alcohols and amines with cleavage of the C-N bond was discovered. The expected products of C-O cleavage are not formed (except as traces in the case of anilides). The reaction proceeds under mild pressure and neutral, homogeneous conditions using a dearomatized, bipyridyl-based PNN Ru(II) pincer complex as a catalyst. The postulated mechanism involves metal-ligand cooperation by aromatization-dearomatization of the heteroaromatic pincer core and does not involve hydrolytic cleavage of the amide. The simplicity, generality, and efficiency of this environmentally benign process make it attractive for the direct transformations of amides to alcohols and amines in good to excellent yields.     

Direct cross-dehydrogenative coupling reactions of imidazopyridines and 1-naphthylamines with ethers under metal-free conditions

Abstract

Convenient, efficient metal-free direct cross-dehydrogenative coupling reactions of imidazopyridines and 1-naphthylamines with ethers were developed. This procedure provided a wide range of valuable, structurally diverse 3-alkyl-imidazopyridine and 4-alkyl-1-naphthylamine derivatives in moderate-to-good yields and with good functional group tolerance.     

Direct amination of pyrimidin-2-yl tosylates with aqueous ammonia under metal-free and mild conditions

Ametal-free synthesis of pyrimidine functionalized primary amines via direct amination of pyrimidin-2-yl tosylate with aqueous ammonia has been developed under mild conditions. The desired products pyrimidin-2-amines can be generated in excellent yields in PEG-400, without any catalysts or other additives.     

Direct oxidative amidation of aldehydes with anilines under mechanical milling conditions

Oxone is found to be an effective oxidant for the oxidative amidation of aldehydes with anilines to furnish amides in a one-pot process under mechanical milling conditions.     

Direct C2-alkylation of azoles with alcohols and ethers through dehydrogenative cross-coupling under metal-free conditions

A metal-free novel, simple, and highly efficient method for the direct C2-alkylation of azoles with alcohols and ethers has been developed on the basis of an oxidative C-H activation process. The dehydrogenative C-C cross-coupling reactions of α-position sp(3) C-H in alcohols and ethers with the 2-position sp(2) C-H in azoles proceeded smoothly in the presence of tert-butyl hydroperoxide (TBHP) under neat reaction conditions, which generated the corresponding products in good yields.     

Direct transformation of benzilic amines to carbonyls using polyacrylamide-bound tungstate under phase-transfer catalysis conditions

A recyclable catalytic system under heterogeneous phase-transfer catalysis conditions was designed by using polyacrylamide-bound tungstate. A convenient method for the oxidative direct transformation of benzilic amines to carbonyls with hydrogen peroxide was then developed.     

Decarboxylation of indole-3-carboxylic acids under metal-free conditions

Abstract

Two reaction systems have been developed for the decarboxylation of indole-3-carboxylic acids. The decarboxylation can be achieved smoothly under K₂CO₃-catalyzed or acetonitrile-promoted basic conditions. It provided an efficient and simple method for the transformation of indole-3-carboxylic acids and the corresponding indoles were isolated with good to excellent yields. From the experimental facts, we put forward the possible reaction mechanism.     

Preparations of N- and P-substituted acetylenes under metal-free conditions

An efficient strategy towards triazole- or phosphine-oxide-substituted alkynes with the assistance of strong base LiHMDS is described. The facile and practical reaction took place from easily prepared substrates in a one-pot manner without participation of any transition metal catalysts or ligands, exhibiting good functional groups tolerance (up to 37 examples) and high efficiency (up to 90% yields). The isolation of the key intermediate proved the hypothesis of the proposed mechanism of the one-pot preparation.     

温和条件下钒催化氧化胺、醇和胺直接合成亚胺(英文)

开发了钒催化氧化胺、醇和胺直接合成亚胺催化体系,无须额外的添加剂或促进剂,空气作为环境友好的氧源,温和条件下,能高收率地得到各种对称和非对称亚胺,并且催化剂非常容易制备和使用.该催化体系对含杂原子亚胺的合成也非常有效.     

Copper-catalyzed direct oxidative C-H amination of benzoxazoles with formamides or secondary amines under mild conditions

A facile, efficient, and practical method for copper-catalyzed direct C-H amination of benzoxazoles with formamides or secondary amines has been developed. The system can be performed in the absence of external base and only requires O(2) or even air as oxidant. A variety of substituted benzoxazol-2-amines were synthesized with moderate to excellent yield.     

One-pot sequential synthesis of 1,2-disubstituted benzimidazoles under metal-free conditions

An easy and inexpensive method has been developed to access 1,2-disubstituted benzimidazoles following a one-pot sequential coupling/reduction/cyclization process under metal-free neutral conditions.     

Progress towards metal-free radical alkylations of quinones under mild conditions

A new method for the radical alkylation of quinones is reported. Lewis basic nitrogen additives increase the efficacy of quinone alkylations from carboxylic acids using catalytic AgNO₃ and Selectfluor as a mild oxidant. Electrochemical data suggests that certain Lewis basic additives are capable of directly reducing Selectfluor through a single-electron transfer, presumably via a charge-transfer complex. This process yields intermediates capable of promoting oxidative decarboxylation of alkyl carboxylic acids without an added metal initiator. Using this strategy, we have demonstrated progress towards a metal-free C–H quinone alkylation reaction that proceeds at room temperature under mild conditions.     

Organocatalytic oxidative dehydrogenation of aromatic amines for the preparation of azobenzenes under mild conditions

(Diacetoxyiodo)benzene used as stoichiometrically and catalytically in the preparation of azobenzenes under mild reaction conditions was developed. The metal-free oxidation systems demonstrated wide substituents tolerance, alkyls, halogens, and several versatile functional groups, such as amino, ethynyl, and carboxyl substituents are compatible well, and the corresponding products could be formed with good to excellent yields. In this disclosed method, the more large scale formation of azo compounds also could be carried out successfully. Of note that 3-ethynylbenzenamine applied as a very useful cross dehydrogenative partner, which coupled with different anilines, providing asymmetrical azo compounds with acceptable yields in one step under very mild reaction conditions.