Mizoroki Heck Coupling Reaction Research Articles

Phosphinocyclodextrins as confining units for catalytic metal centres. Applications to carbon-carbon bond forming reactions.

The capacity of two cavity-shaped ligands, HUGPHOS-1 and HUGPHOS-2, to generate exclusively singly phosphorus-ligated complexes, in which the cyclodextrin cavity tightly wraps around the metal centre, was explored with a number of late transition metal cations. Both cyclodextrin-derived ligands were assessed in palladium-catalysed Mizoroki–Heck coupling reactions between aryl bromides and styrene on one hand, and the rhodium-catalysed asymmetric hydroformylation of styrene on the other hand. The inability of both chiral ligands to form standard bis(phosphine) complexes under catalytic conditions was established by high-pressure NMR studies and shown to have a deep impact on the two carbon–carbon bond forming reactions both in terms of activity and selectivity. For example, when used as ligands in the rhodium-catalysed hydroformylation of styrene, they lead to both high isoselectivity and high enantioselectivity. In the study dealing with the Mizoroki–Heck reactions, comparative tests were carried out with WIDEPHOS, a diphosphine analogue of HUGPHOS-2.

Synthesis and activity evaluation of a FeCl2-promoted palladium hollow nano-sphere heterogeneous catalyst in Mizoroki–Heck coupling reactions

A high-active, high-quality, and high-yield hollow Pd–PVP–Fe (palladium–poly(N-vinylpyrrolidone)–iron) nano-sphere catalyst with cubic structure was synthesized via a cheap method without using any support. This catalyst exhibited excellent catalytic activity in the Mizoroki–Heck reactions of less reactive chlorobenzene and some aryl bromides with n-butyl acrylate. The catalyst was fully characterized using SEM (scanning electron microscopy), EDX (energy dispersive X-ray spectroscopy), TEM (transmission electron microscopy), HRTEM (high resolution TEM), SAED (selected area electron diffraction) pattern, XRD (X-ray diffraction spectroscopy), FT-IR (Fourier transform infrared spectrophotometry), UV–Vis Spectrophotometry, Zeta sizer, and AAS (atomic absorption spectrometry). Effects of FeCl2·4H2O and PVP concentrations as well as their compatibility with palladium in the catalytic system were investigated. The catalytic property of the catalyst can be controlled by adjusting the proportion of Fe0, Pd0, and PVP concentration. The reused catalyst showed excellent activity as well as negligible leaching of the metal nanostructures into solution from the catalyst system.

Bis(functionalized NHC) Palladium(II) Complexes via a Postmodification Approach

A series of 20 bis(functionalized NHC) Pd(II) complexes have been conveniently synthesized through postmodification reactions of the common parent NHC complexes trans-[PdBr2(C3Br-bimy)2] (1a) and trans-[PdBr2(C3Br-imy)2] (1b) (C3Br-bimy = 1-benzyl-3-(3-bromopropyl)benzimidazolin-2-ylidene and C3Br-imy = 1-benzyl-3-(3-bromopropyl)imidazolin-2-ylidene) with an N-C3Br tether. Depending on the nature of the nucleophiles added, competing bromido ligand displacements also occurred. In comparison to the conventional access to functionalized NHC complexes, which involves metalation of individually prefunctionalized azolium salts, this highly modular method proves more effective in cost and time savings. The tetraalkylammonium-functionalized complex trans-[PdBr2(C3NEt3-bimy)2]Br2 (14) as a product of the second-generation postmodification of complex 1a was also tested for its catalytic activity in Mizoroki–Heck coupling reactions to study and model the effect of a catalytic amount of ammonium salt additive in Pd-c...

Imidazole, pyrimidine and diazepine containing heteroaryl-substituted heterocyclic salts as efficient ligand precursors for Mizoroki–Heck coupling reaction: synthesis, structural characterization and catalytic activities

The nine new heteroaryl-substituted imidazolidinium (1a–c), pyrimidinium (2a–c) and diazepinium (3a–c) salts as N-heterocyclic carbene (NHC) precursors were synthesized in good yields and entirely characterized using elemental analyses and conventional spectroscopic methods. In situ formed complexes from heterocyclic salts (1–3), Pd(OAc)2 and in the presence of KOBut as a base were tested as catalysts for the Mizoroki–Heck coupling reaction in an aqueous media and very high yields were achieved. 1,3-Di(5-methylthiophen-2-ylmethyl)pyrimidinium hexafluorophosphate salt (2b) was structurally characterized by single-crystal X-ray diffraction. In the 2b compound (C16H21N2S2)+[PF6]−, the terminal thiophene rings are twisted with a dihedral angle of 72.8(3)°. In the pyrimidine ring, the three successive C atoms between the N atoms are disordered over two positions [occupancy ratio 0.753(12):0.247(12)]. In the crystal, neighboring molecules are linked by C–H…F hydrogen bonds, running along the b axis.

Supported Pd nanoparticles on Mn-based metal–organic coordination polymer: Efficient and recyclable heterogeneous catalyst for Mizoroki–Heck cross coupling reaction of terminal alkenes

Supported palladium nanoparticles on Mn-carboxylate coordination polymer (Pd/MnBDC) were prepared using solution impregnation method. This new catalyst was characterized by XRD, SEM, TEM, EDX, XPS, FTIR and TGA analysis. The Pd/MnBDC exhibits efficient catalytic activity for the Mizoroki–Heck coupling reaction between iodobenzene and either aromatic or aliphatic terminal alkenes and reuses up to four runs without significant loss of activities.

Synthesis of Cinchona Alkaloid-Derived Chiral Polymers by Mizoroki–Heck Polymerization and Their Application to Asymmetric Catalysis

To facilitate the asymmetric catalysis process, we designed novel polymeric chiral catalysts. Since quaternary ammonium salts of cinchona alkaloid derivatives show efficient catalytic activity in various asymmetric transformations, we have synthesized novel chiral polymer catalysts containing cinchonidinium moieties in the main chain of the polymer. Repetitive Mizoroki–Heck coupling reactions between the cinchona alkaloid-derived dimer and diiodide afforded the chiral polymer catalysts, which were subsequently used as catalysts in asymmetric benzylation reactions to yield the corresponding phenylalanine derivatives in higher yields and levels of enantioselectivity than can be obtained with a monomeric catalyst. Because of the insolubility of the polymeric catalysts, they were easily recovered from the reaction mixture and reused several times.

ChemInform Abstract: Revisiting Heck‐Mizoroki Reactions in Ionic Liquids

AbstractReview: 107 refs.

Synthesis and catalytic activity of pyrazolyl-functionalized N-heterocyclic carbene palladium complexes

Three pyrazolyl-functionalized N-heterocyclic carbene (NHC) palladium complexes based on 1-[2-(pyrazol-1-yl)phenyl]imidazole have been synthesized and characterized by physico-chemical and spectroscopic methods, and the structures of two of the complexes have been confirmed by single-crystal X-ray diffraction. The pyrazolyl-functionalized NHCs act as chelating N,C-bidentate ligands in these three complexes. Catalytic tests have proved that these complexes exhibit highly effective catalytic activity for the Suzuki–Miyaura and Mizoroki–Heck coupling reactions in water or aqueous/organic media under air. The substituents on the pyrazolyl ring exert different influences on the catalytic activity of the complexes in these coupling reactions.

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.

ChemInform Abstract: PdCl2(1‐Methylimidazole)2‐Catalyzed Suzuki—Miyaura and Mizoroki—Heck Reactions Performed in Neat Water.

AbstractA high yielding Suzuki—Miyaura and Mizoroki—Heck coupling reaction with water as solvent and PdCl2(1‐Methylimidazole)2 complex as catalyst is shown.

Synthesis, structural characterization and catalytic activity of benzimidazole‐functionalized Pd(II) N‐heterocyclic carbene complexes

AbstractTwo Pd(II)–NHC complexes bearing benzimidazole and pyridine groups have been successfully prepared and fully characterized by NMR and X‐ray diffraction analysis. The structure of palladium complexes are a typical square‐planar with palladium surrounded by two pairs of trans‐arranged benzimidazole and carbene ligands. The Pd–NHC complexes have been proved to be a highly efficient catalyst for the Mizoroki–Heck coupling reaction of aryl halides with various substituted acrylates under mild conditions in excellent yields. Copyright © 2013 John Wiley & Sons, Ltd.

Mizoroki–Heck coupling reactions of arenediazonium tetrafluoroborate salts catalyzed by aluminium hydroxide-supported palladium nanoparticles

Mizoroki–Heck cross-couplings of arenediazonium tetrafluoroborate salts catalyzed by highly active aluminium hydroxide-supported palladium nanoparticles catalyst have been investigated for the first time. The reactions are performed at 25°C in EtOH without any base and ligand to afford the corresponding coupling products in good to excellent yields under non-anhydrous and non-degassed conditions.

Revisiting Heck–Mizoroki reactions in ionic liquids

The use of ionic liquids as an alternative to conventional organic solvents has been an important research topic in order to answer economic and environmental challenges. This critical review revisits the different approaches and achievements on the use of ionic liquids as solvents in Heck–Mizoroki coupling reactions; a brief reference to supported ionic liquids will be also highlighted.

Chugaev‐type bis(acyclic diaminocarbenes) as a new ligand class for the palladium‐catalyzed Mizoroki–Heck reaction

A series of differently substituted Chugaev‐type palladium bis(acyclic diaminocarbene) complexes was screened to identify the most active catalyst for Mizoroki–Heck coupling reactions of aryl bromides with styrene. The best catalyst, which contains three methyl groups on the bis(carbene) ligand, gives excellent coupling yields at 120 °C for both activated and deactivated aryl bromides. However, activity with aryl chlorides is limited to electron‐deficient examples. The optimized catalyst demonstrates limited air and moisture stability, giving reduced yields in couplings of activated aryl bromides in open‐flask conditions. The modular synthesis of this class of catalysts should allow further fine‐tuning of activity in Mizoroki–Heck and related coupling reactions. Copyright © 2012 John Wiley & Sons, Ltd.

Synthesis and biological evaluation of novel (E) stilbene-based antitumor agents

Several new (E) stilbenes were synthesized by a combination of a Wittig olefination followed by Mizoroki–Heck coupling reactions. These compounds were screened for antitumor activity in a panel of 8 human cancer cell lines by a colorimetric SRB assay. Several of these compounds exhibit strong cytotoxicity. The most active compound of this series showed an average IC50 value of 0.03 μmol; it acts by apoptosis as shown by a dye-exclusion test, an extra acridine orange/ethidium bromide staining and DNA-laddering experiments.

Synthesis of Large Polycyclic Aromatic Hydrocarbons from Bis(biaryl)acetylenes: Large Planar PAHs with Low π-Sextets

A new synthesis of large PAHs with low Clar sextets was developed. This synthesis involves initial bis(biaryl)acetylene 1, which undergoes initial ICl-aromatization and a subsequent Mizoroki-Heck coupling reaction to give dibenzochrysene derivative 3 that can be transformed into planar PAHs 4 using DDQ-oxidation.

ChemInform Abstract: Pyrazolin‐4‐ylidenes: A New Class of Intriguing Ligands

AbstractReview: 39 refs.

Synthesis of chiral mono(N-heterocyclic carbene) palladium and gold complexes with a 1,1'-biphenyl scaffold and their applications in catalysis.

Axially chiral mono(NHC)–Pd(II) and mono(NHC)–Au(I) complexes with one side shaped 1,1'-biphenyl backbone have been prepared from chiral 6,6'-dimethoxybiphenyl-2,2'-diamine. The complexes were characterized by X-ray crystal structure diffraction. The Pd(II) complex showed good catalytic activities in the Suzuki–Miyaura and Heck–Mizoroki coupling reactions, and the (S)-Au(I) complexes also showed good catalytic activities in the asymmetric intramolecular hydroamination reaction to give the corresponding product in moderate ee.

Labeling of alprenolol with fluorescent aryl iodide as a reagent based on Mizoroki–Heck coupling reaction

A novel fluorescent labeling method for alprenolol was developed based on Mizoroki–Heck coupling reaction. We designed and synthesized fluorescent aryl iodide, 4-(4,5-diphenyl-1 H-imidazol-2-yl)iodobenzene (DIBI) as a labeling reagent. DIBI has a lophine skeleton carrying an iodide atom acting as fluorophore and reactive center, respectively. In order to evaluate the usefulness of DIBI, a high-performance liquid chromatography (HPLC) with fluorescence detection method was developed for the determination of alprenolol as a model compound of terminal double bond. The fluorescent labeling of alprenolol with DIBI was achieved in the presence of palladium acetate as a catalyst, and the labeled alprenolol was detected fluorometrically. In addition, it was found that the fluorescence of DIBI derivative increased and red shifted when compared with that of DIBI. Furthermore, the proposed method could be applied to determine the alprenolol concentration in rat plasma after administration of alprenolol without interferences from biological components. The detection limit (S/N = 3) for alprenolol in rat plasma was 0.74 ng/mL (30 fmol on column).

Pyrazolin-4-ylidenes: a new class of intriguing ligands

The immense success of N-heterocyclic carbenes in recent years has initiated the search for even stronger ligands leading to the discovery of abnormal and remote NHCs. This article reflects our particular interest in the coordination chemistry of pyrazolin-4-ylidenes as a contribution to this field. A modular approach to 4-iodopyrazolium salts with different substitution patterns is described, which upon oxidative addition to Pd(0) gave rise to a library of new Pd(ii) pyrazolin-4-ylidene complexes. A preliminary study showed that selected complexes are active precatalysts in Suzuki-Miyaura and Mizoroki-Heck coupling reactions. The 3,5-substituents of pyrazolin-4-ylidenes are found to have significant effects on complexation and catalytic activities. Finally, the nature of this new class of ligands is discussed, and a future direction for further explorations in this exciting field is envisioned.