Microwave-assisted synthesis of 2-acetyl-5-arylthiophenes and 4-(5-arylthiophen-2-yl)thiazoles via Suzuki coupling in water

Abstract

2-Acetyl-5-bromothiophene and 4-(5-bromothiophen-2-yl)-2-methyl-1,3-thiazole, as deactivated bromide candidates, were prepared and used for Suzuki cross-coupling reactions with a number of aryl(hetaryl)boronic acids in water or DMF as solvents. The cross-coupling reactions were carried out under thermal heating as well as microwave irradiating conditions using a benzothiazole-based Pd(II)-precatalyst. Optimization of the catalytic reaction condition was also studied.

Efficient and Recyclable Solid-Supported Pd(II) Catalyst for Microwave-Assisted Suzuki Cross-Coupling in Aqueous Medium

“…Chitosan is a non-toxic, biodegradable, and eco-friendly biopolymer and is commonly obtained from the deacetylation reaction of chitin (a long-chain polymer of N -acetylglucosamine). − Heterogeneous palladium catalysts have been characterized by their elevated catalytic sites, high selectivity, possibility to regulate the catalyst chemo-, regio-, and enantio-selectivities, ease of optimization of the catalytic systems, and better yields and are extensively used in Suzuki coupling reactions. − In addition, heterogeneous catalysts are superior over homogeneous ones, which suffer from major problems such as difficult separation and recovery and sometimes result in non-acceptable contaminations in the reaction products. − The expensive ligands employed in Suzuki coupling reactions were also problematic; therefore, numerous cheap materials, for example, silica, carbon, zeolite, cellulose, and chitosan had been involved as alternative support materials. − Among these, chitosan was preferred due to its unique properties such as (1) low cost, (2) abundance, (3) environmental friendliness, (4) renewability, and (5) the presence of the reactive −NH 2 and −OH functions capable of further modifications of chitosan. , Palladium-catalyzed Suzuki–Miyaura cross-coupling reactions were widely incorporated in organic chemistry. − The use of a microwave (MW) irradiation platform had high impacts in the academia and industry. − Furthermore, conducting organic reactions in aqueous solvents was advantageous compared to that in organic solvents. , As part of our interest on the applications of various palladium­(II) complexes in C–C cross-coupling reactions, − the present work aimed at the facile synthesis of a chitosan-based palladium­(II) biopolymer complex (denoted hereafter as ChsB-Pd 3 ) as a heterogeneous solid-nanosized catalyst and to study its catalytic activity in Suzuki cross-coupling reactions under the traditional heating mode as well as using the MW irradiation tool. In the presence of this heterogeneous catalyst, high conversion of different biaryls was achieved.…”

Microwave-assisted chemoselective synthesis and photophysical properties of 2-arylazo-biphenyl-4-carboxamides from hydrazonals

“…[56][57][58] The straightforward amidation of carboxylic acids was successfully modied by microwave activation. [59][60][61][62][63][64][65] Therefore, in continuation of our research interest in microwave-assisted organic synthesis, [66][67][68][69][70][71][72][73][74][75][76][77] herein we re-investigated our previous work on a supplemental reaction of 3-oxo-2-arylhydrazonopropanals 1 with acetoacetanilide 2, 68 by optimization of reaction conditions (components' molar ratios, solvents, bases and activation modes) towards chemoselective construction of the 2-(arylazo)-5-hydroxy-N-phenyl-[1,1 ′ -biphenyl]-4-carboxamide derivatives 3 instead of the cinnoline derivatives 4 (Scheme 1) and the photophysical properties of the obtained biphenyl-4-carboxamides were evaluated. The structures of the new products were characterized by IR, 1 H-and 13 C-NMR, MS and HRMS spectral data as well as Xray single crystallography of selected examples.…”

Microwave promoted Heck and Suzuki coupling reactions of new 3-(5-bromobenzofuranyl)pyrazole in aqueous media

“…In continuation of our research work on the use of palladium(II) complexes under microwave irradiation for Suzuki-Miyaura, Heck-Mizoroki, and Sonogashira cross-coupling reactions, [33][34][35][36][37][38][39][40][41][42][43][44] we report, herein, the use of the benzothiazole-oxime palladium(II) complex (4) as a pre-catalyst for the Suzuki-Miyaura and Heck-Mizoroki cross-coupling reactions of 3-(5-bromobenzofuran-2-yl)-1H-pyrazole (3) under thermal heating and microwave irradiation in aqueous media.…”