Sustainable synthesis of azobenzenes, quinolines and quinoxalines via oxidative dehydrogenative couplings catalysed by reusable transition metal oxide–Bi(iii) cooperative catalysts

Heterogeneous catalytic oxidative dehydrogenative processes for N-heterocycles are presented, which enable waste-minimized (additive-, oxidant-, base-free), efficient cyclisations/couplings via transition metal oxide–Bi(iii) cooperative catalysis.

Environmentally Friendly Nafion-Catalyzed Synthesis of Substituted 2-Ethyl-3-Methylquinolines from Aniline and Propionaldehyde under Microwave Irradiation

Herein, we report a facile synthetic methodology for the preparation of 2,3-dialkylquinolines from anilines and propionaldehydes. This cyclization involved environmentally friendly Nafion® NR50 as an acidic catalyst with microwave irradiation as the heating source. A series of substituted 2-ethyl-3-methylquinolines were prepared from various anilines and propionaldehyde derivatives through this protocol with good to excellent yields. Some new chemical structures were confirmed by X-ray single-crystal diffraction analysis and the related data were provided. The plausible reaction mechanism studies are also discussed.

Acceptorless dehydrogenative condensation: synthesis of indoles and quinolines from diols and anilines

The use of diols and anilines as reagents for the preparation of indoles represents a challenge in organic synthesis. By means of acceptorless dehydrogenative condensation, heterocycles, such as indoles, can be obtained. Herein we present an experimental and theoretical study for this purpose employing heterogeneous catalysts Pt/Al2O3 and ZnO in combination with an acid catalyst (p-TSA) and NMP as solvent. Under our optimized conditions, the diol excess has been reduced down to 2 equivalents. This represents a major advance, and allows the use of other diols. 2,3-Butanediol or 1,2-cyclohexanediol has been employed affording 2,3-dimethyl indoles and tetrahydrocarbazoles. In addition, 1,3-propanediol has been employed to prepare quinolines or natural and synthetic julolidines.

New advances in the catalysis of organic reactions by iron compounds

The review summarizes and systematizes the literature data on a new promising application area of iron compounds, that is, catalysis of organic reactions. The considered reactions include halogenation, formation of C−C bonds with the participation of various substrates, new methods for the synthesis of ethers and aromatic and heteroaromatic carboxylic acid esters, N-alkylation of aliphatic and aromatic amines and amidation of olefins and cyclopropane-containing hydrocarbons. The advances in the synthesis of quinolines and unusual cyclization reactions catalyzed by iron complexes are described.

The bibliography includes 144 references.

Production of 1,3-Propanediol from Pure and Crude Glycerol Using Immobilized Clostridium butyricum

The present study describes the production of the value-added chemical 1,3-propanediol (1,3-PD) from crude glycerol, a waste by-product formed during biodiesel production. The efficiency, robustness, and stability of the process were improved by immobilization of the anaerobic bacterium Clostridium butyricum into a polyvinyl alcohol (PVA) hydrogel. The highest average productivity, 6.8 ± 0.2 g/(L·h), was achieved in 10 consecutive, repeated batch fermentations, with an initial concentration of pure glycerol 45.5 ± 0.7 g/L, after 2.5 hours. The highest final concentration and yield of 1,3-PD, 28.3 ± 0.6 g/L, and 0.42 ± 0.01 g/g, respectively, were achieved in eleven repeated batch fermentations, after increasing the initial pure glycerol concentration to 70.4 ± 1.9 g/L. Two different types of crude glycerol, produced from used cooking oil (UCO) and rapeseed oil (RO), were tested in repeated batch fermentations, with an average productivity achieved of 2.3 ± 0.1 and 3.5 ± 0.3 g/(L·h), respectively. The highest final concentration and yield of 1,3-PD, 12.6 ± 0.9 g/L, and 0.35 ± 0.02 g/g, respectively, were observed in fifteen repeated batch fermentations with RO crude glycerol. An excellent stability of the immobilized anaerobic bacteria and increase of productivity in fermentation of crude glycerol was demonstrated.

An efficient 3-acylquinoline synthesis from acetophenones and anthranilviaC(sp3)–H bond activation mediated by Selectfluor

An efficient method for the synthesis of 3-functionalized quinolines from commercially available acetophenones and anthranil has been described. Selectfluor propels the C(sp³)–H bond activation of the acetophenones and aza-Michael addition of anthranil resulting in annulated 3-acylquinolines in moderate to high yields. DMSO acts not only as a solvent but also as a one carbon donor in the reaction.

An efficient method for the synthesis of 3-functionalized quinolines from acetophenones and anthranil mediated by Selectfluor was achieved.

Recent Progress in the Transition Metal Catalyzed Synthesis of Indoles

Indole is the most frequently found heterocyclic core structures in pharmaceuticals, natural products, agrochemicals, dyes and fragrances. For about 150 years, chemists were absorbed in finding new and easier synthetic strategies to build this nucleus. Many books and reviews have been written, but the number of new syntheses that appear in the literature, make necessary continuous updates. This reviews aims to give a comprehensive overview on indole synthesis catalyzed by transition metals appeared in the literature in the years 2016 and 2017.

Inhibitors of the Detoxifying Enzyme of the Phytoalexin Brassinin Based on Quinoline and Isoquinoline Scaffolds

The detoxification of the phytoalexin brassinin to indole-3-carboxaldehyde and S-methyl dithiocarbamate is catalyzed by brassinin oxidase (BOLm), an inducible fungal enzyme produced by the plant pathogen Leptosphaeria maculans. Twenty-six substituted quinolines and isoquinolines are synthesized and evaluated for antifungal activity against L. maculans and inhibition of BOLm. Eleven compounds that inhibit BOLm activity are reported, of which 3-ethyl-6-phenylquinoline displays the highest inhibitory effect. In general, substituted 3-phenylquinolines show significantly higher inhibitory activities than the corresponding 2-phenylquinolines. Overall, these results indicate that the quinoline scaffold is a good lead to design paldoxins (phytoalexin detoxification inhibitors) that inhibit the detoxification of brassinin by L. maculans.

Assembly of Diversely Substituted Quinolines via Aerobic Oxidative Aromatization from Simple Alcohols and Anilines

An aerobic oxidative aromatization of simple aliphatic alcohols and anilines under the Pd(OAc)₂/2,4,6-Collidine/Brønsted acid catalytic system has been established, providing a direct approach for the preparation of diverse substituted quinoline derivatives in high yields with wide functional group tolerance. Practically, the protocol can be easily scaled up to gram-scale and was utilized in the concise formal synthesis of a promising herbicide candidate.

Palladium-catalyzed synthesis of quinolines from allyl alcohols and anilines

A process for quinoline synthesis through palladium-catalyzed oxidative cyclization of aryl allyl alcohols and anilines is described.

Catalytic Synthesis of Substituted Indoles and Quinolines from the Dehydrative C-H Coupling of Arylamines with 1,2- and 1,3-Diols

The cationic ruthenium-hydride complex catalyzes dehydrative C-H coupling reaction of arylamines with 1,2-diols to form the indole products. The analogous coupling of arylamines with 1,3-diols afforded the substituted quinolines. The catalytic method directly forms these coupling products in a highly regioselective manner without generating any toxic byproducts.

Ruthenium-Catalyzed Amination of Secondary Alcohols using Borrowing Hydrogen Methodology

A new ruthenium complex catalyzes the amination of primary and secondary alcohols and the regioselective mono- and sequential diamination of diols via the borrowing hydrogen pathway. Several variations on new intra- and intermolecular cyclizations of aminoalcohols, diols and diamines lead to heterocyclic ring systems.

Synthesis of quinolines through copper-catalyzed intermolecular cyclization reaction from anilines and terminal acetylene esters

A simple and convenient copper-catalyzed intermolecular cyclization reaction for the synthesis of quinolines from anilines and terminal acetylene esters has been developed.

Ruthenium-catalysed C-alkylation of 1,3-dicarbonyl compounds with primary alcohols and synthesis of 3-keto-quinolines

Mono alkylation of 1,3-dicarbonyls is now possible with alcohols and catalytic amount of Hantzsch ester under Ru catalysis.

An annulative transfer hydrogenation strategy enables straightforward access to tetrahydro fused-pyrazine derivatives

A ruthenium-catalyzed annulative transfer hydrogenation strategy, enabling straightforward access to tetrahydro fused-pyrazine derivatives from N-heteroaryl diamines and vicinal diols, is demonstrated.

Iron-catalyzed amination of alcohols assisted by Lewis acid

An efficient Lewis acid-assisted, iron-catalyzed amination of alcohols using borrowing hydrogen methodology was developed. In particular, silver fluoride was identified to be a highly effective additive to overcome the low efficiency in the amination of secondary alcohols catalyzed by Knölker's complex.

Synthesis of unsymmetric tertiary amines via alcohol amination

The first one-pot selective synthesis of unsymmetric tertiary amines is reported by the amination of two types of alcohols with primary amines via the development of a simple CuAlOx-HT catalyst and enables the synthesis of unsymmetric amines in a wide variety of primary amines and alcohols.

An atom economical method for the direct synthesis of quinoline derivatives from substituted o-nitrotoluenes

A one-pot procedure for the preparation of substituted quinolines from substituted o-nitrotoluenes with electron-withdrawing groups and olefins (acrylic esters and acrylonitriles) using a cesium catalyst under mild reaction conditions is reported. The process involves a [2+4] cycloaddition mechanism.

Rhodium-catalyzed synthesis of quinolines and imines under mild conditions

An efficient protocol for the synthesis of quinolines in aqueous medium using a Rh(ii)acetate/TPPTS recyclable catalytic system has been developed. Furthermore, imines were also synthesized from benzylamines in moderate to good yields under solvent free conditions.