This article presents a review of the most significant developments with N-heterocyclic carbene (NHC)–palladium catalytic systems used for the Heck reaction. For more than the past two decades, a large number of new NHC–Pd complexes have been synthesized and characterized. These studies focused on NHCs as a phosphine analogue, but the current review highlights the differences with particular ligands so as to attain a suitable balance between the electronic and bulky environments around the metal. NHCs have gained wide recognition as these ligands act as excellent σ-donors that form stable metal–NHCs with strong metal–carbon bonds. For this reason, metal–NHCs are commonly used as they are highly reactive and can selectively serve as catalysts for various chemical transformations. The objective of our article is to highlight significant recent progress in NHC–Pd(II) complexes and provide an overview of their extensive interaction in the Mizoroki–Heck reaction. © 2017 Académie des sciences

Pundlik Rambhau Bhagat

Department of Chemistry

School of Advanced Sciences

Vellore Campus

Balinge K.R

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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Comptes Rendus Chimie

In this work, the catalytic performance of a polymer-supported Pd(II)-salen complex (PS-Pd-salen) as an effective and environmentally friendly catalyst for the Mizoroki-Heck C[sbnd]C cross-coupling reaction is presented. The PS-Pd-salen complex was employed as a catalyst for Mizoroki-Heck reactions of an aryl halide with various terminal alkenes (Styrene, Methyl acrylate, Ethyl acrylate, n-butyl acrylate, tert-Butyl acrylate) under phosphine free conditions. Moreover, a range of Mizoroki-Heck reactions using different polar solvents, co-solvents, and bases has been investigated. Aryl iodides and bromides with terminal alkene are well activated in C[sbnd]C coupling reactions. All products were isolated by column chromatography as liquids/white to off-white crystalline solids and confirmed by 1H and 13C NMR spectroscopy. The catalyst could be easily separated by filtrations and reusability of catalyst was also assessed under optimized conditions. The hot filtration test revealed that the catalyst was truly heterogeneous, very active and stable under the reaction conditions and could be reused up to fifth cycles with analogous activities to that of the fresh catalyst. High catalytic activity at a low concentration (30 mg) and flexibility under mild reaction conditions, simple product work-up towards Mizoroki-Heck reactions indicated that PS-Pd-salen was an efficient catalyst for C[sbnd]C coupling reactions. © 2019 Elsevier B.V.

Inorganica Chimica Acta

A polymer-supported salen-palladium complex as a heterogeneous catalyst for the Mizoroki-Heck cross-coupling reaction

A polymer supported Pd-salen complex (PS-Pd-salen) was synthesized and characterized by Fourier transform infrared spectroscopy (FT-IR), Fourier-transform NMR spectroscopy (FT-NMR), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), surface area and pore size distribution by Brunauer-Emmett-Teller (BET). The heterogeneous catalytic performance of the PS-Pd-salen for the Suzuki-Miyaura coupling of variety of phenyl boronic acid with different aryl halides was successfully conducted in water with K2CO3 and 20 mg catalyst loading at room temperature. The coupling reactions with aryl iodides and bromides were achieved at room temperature with good to excellent yield; whereas the reactions with aryl chlorides were performed in aqueous-ethanol (1:1) at 90 °C. The product yields related with the substrates were optimized, and main reaction factors influencing the yields were also recognized. The results clearly indicated that the reaction constraints needed to achieve high yields are substrate-reliant. The hot filtration test verified heterogeneous nature of PS-Pd-salen complex. Moreover, the catalyst showed excellent reusability for five successive runs in slight compromising with its activity. © 2017 Elsevier B.V.

Journal of Organometallic Chemistry

A highly recoverable polymer-supported ionic salen-palladium complex as a catalyst for the Suzuki-Miyaura cross coupling in neat water

A series of palladium acyclic diaminocarbene (ADC) complexes of the type;cis-[((RNH)-N-1)(R-2)methylidene]-PdCl2(CNR1) [R-1 =;2,4,6-(CH3)(3)C6H2: R-2 = NC5H10 (2); NC4H8 (3); NC4H8O (4)] were used;not only to perform the C-sp(2)-C-sp Hiyama coupling between aryl iodide;and triethoxysilylalkynes but also to subsequently carry out the one-pot;tandem Hiyama alkynylation/cyclization reaction between 2-iodophenol and;triethoxysilylalkynes, giving a convenient time-efficient access to the;biologically relevant benzofuran compounds. The palladium ADC complexes;(2-4) were conveniently synthesized by the nucleophilic addition of;secondary amines, namely, piperidine, pyrrolidine, and morpholine on the;cis-\(2,4,6-(CH3)(3)C6H2)NC\(2)PdCl2 in moderate yields (ca. 61-66\%).

Fulltext

Acs Omega

One-Pot Tandem Hiyama Alkynylation/Cyclizations by Palladium(II) Acyclic;Diaminocarbene (ADC) Complexes Yielding Biologically Relevant Benzofuran;Scaffolds

Silver(I) and palladium(II) complexes of new pentamethylene-functionalized bis-imidazolium dication ligands and its application in Heck and Suzuki–Miyaura coupling reaction

Benzimidazol-2-ylidene ligated palladacyclic complexes of N,N-dimethylbenzylamine – Synthesis and application to C–C coupling reactions

Tetrahedron

Synthesis of surface-active N -heterocyclic carbene ligand and its Pd-catalyzed aqueous Mizoroki–Heck reaction

Tetrahedron Letters

Synthesis of novel pillar[5]arene-based N -heterocyclic carbene ligands for Pd-catalysed Heck reactions

Well-defined palladium N-heterocyclic carbene (NHC) complexes were employed in the one-pot tandem Heck alkynylation/cyclization sequence for preparing biologically relevant benzofuran compounds under copper-free conditions in a time-efficient step-reduced fashion. In particular, a series of binuclear palladium complexes, 1b-1e and 2b-2e, of the alkyl-bridged NHC ligands, namely, {1,1′-di-R1-4,4′-R2-di-1,2,4-triazoline-5,5′-diylid-2-ene] (R1 = i-Pr; R2 = -(CH2)2-, -(CH2)3-), and their mononuclear analogues, trans-(NHC)PdBr2(pyridine) (3b) and cis-(NHC)PdBr2(PPh3) (3c), successfully catalyzed the one-pot tandem Heck alkynylation/cyclization reaction of 2-iodophenol with a variety of terminal alkyne substrates, yielding 2-substituted benzofuran derivatives. The mononuclear complexes 3b and 3c were nearly half as active as the representative dinuclear analogue 1c under analogous reaction conditions, thereby implying that, at the same mole percent of the palladium loading, the monometallic 3b and 3c and the bimetallic 1c complexes were equally effective as catalysts. The two sites of the bimetallic complex 1c performed as two separate independent catalytic sites, displaying no cooperativity effect in the catalysis. Finally, the practical utility of the aforementioned catalysts was demonstrated for a representative catalyst 1c through the convenient synthesis of a key intermediate, 3-[2-(benzo[d][1,3]dioxol-5-yl)-7-methoxybenzofuran-5-yl]propan-1-ol, in a total-synthesis protocol of the natural product Egonol. © 2016 American Chemical Society.

Inorganic Chemistry

Accessing a Biologically Relevant Benzofuran Skeleton by a One-Pot Tandem Heck Alkynylation/Cyclization Reaction Using Well-Defined Palladium N-Heterocyclic Carbene Complexes

Journal	Data powered by TypesetComptes Rendus Chimie
Publisher	Data powered by TypesetElsevier BV
ISSN	1631-0748
Open Access	No