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

Abstract

Suzuki-Miyaura and Mizoroki-Heck cross-coupling reactions of 3-(5-bromobenzofuran-2-yl)-1H-pyrazole with various arylboronic acids and terminal olefins, respectively, were investigated using a benzothiazole-oxime palladium(II) complex, under both thermal and microwave-irradiation conditions, in an open vessel, using aqueous solvent. The benzothiazole-oxime-based Pd(II) complex was found to be an efficient, and highly active pre-catalyst for the cross-coupling reactions, and for the preparation of new C-C cross-coupled compounds of potential biological interest which are difficult to obtain using other synthetic routes.

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.…”

Transition‐metal‐catalyzed Heteroannulation Reactions in Aqueous Medium

“…[73][74][75][76][77] In addition, our research interest was focused on the applications of palladium catalysts in CÀ C cross-coupling reactions in water under microwave irradiation. [78][79][80][81][82][83][84][85][86][87] The current review article is specifically focusing on heteroannulation reactions (i. e. synthesis of fused heterocycles) employing transition-metal catalysts under different activation modes in the presence of water. Heteroannulation (fusion) of functionalized aromatic or heteroaromatic compounds via CÀ H activations concurrent with inter-or intramolecular heterocyclization in the presence of transition-metal catalysts leads to construction of new fused-heterocycles with, in most cases, interesting application and biological values.…”

“…Several collective reviews outlined the sustainability of metal catalysts for organic reactions in aqueous solvents [73–77] . In addition, our research interest was focused on the applications of palladium catalysts in C−C cross‐coupling reactions in water under microwave irradiation [78–87] . The current review article is specifically focusing on heteroannulation reactions ( i. e .…”

Benzothiazole-Based Palladium Complexes as Efficient Nano-Sized Catalysts for Microwave Hydrothermal Suzuki –Miyaura Cross-Couplings

“…Experimentally, using microwaves as a power source for performing organic transformations was received a great interest due to its attainments in green methodologies especially that use water as a reaction medium [18][19][20][21]. In extension to our efforts in the eld of developing a new nitrogen containing heterocyclic ligands and using their palladium (II) complexes in many carbon-carbon cross coupling reactions [22][23][24][25][26], we explore in this work the synthesis of novel nano-sized benzothiazole-based Pd (II) complexes 4a,b (Scheme 2) and studying their catalytic e ciency in carboncarbon cross coupling reactions aryl halides with aryl boronic acids under microwaves irradiations in aqueous medium. example, the proton NMR spectrum of the 3a showed the resonance of protons of the two methyl groups of N(Me) 2 group as two singlet signals at δ 3.00 and 3.14ppm and two sets of triplets at δ 7.13 and 7.28 ppm with coupling constant J = 8.5 Hz due to the two-aromatic ring (CH) protons.…”