Heck Mizoroki Research Articles

Polymer-Supported Bis-1,2,4-triazolium Ionic Tag Framework for an Efficient Pd(0) Catalytic System in Biomass Derived γ-Valerolactone

A resin-bound 1,2,4-triazolium ionic tag has been used as support for the preparation of solid palladium nanoparticles (Pd(0)-POLI-TAG-Pd). Owing to the pincer-type architecture of the triazolium ligand, the stabilization of a high amount of palladium nanoparticles (16 wt %) has been possible. The catalytic system has been fully characterized and used in low amounts (i.e., 0.1 mol % palladium loading) in representative Heck–Mizoroki cross-coupling processes. A negligible release of the metal was demonstrated, and a high activity was obtained over more runs. Besides, the protocol has been optimized for the use of safe biomass-derived γ-valerolactone reaction medium.

Convenient and efficient Suzuki–Miyaura and Heck–Mizoroki cross-coupling reactions catalyzed by 1,3,4-trisubstituted-1,2,3-triazolium iodide and palladium salt systems

A series of 1,3,4-trisubstituted-1,2,3-triazolium iodide salts (4a–c) were synthesized via a three-step reaction sequence. Corresponding anilines (1a–c) were converted to azides (2a–c) which were then treated with phenylacetylene with “Click” chemistry to access 1,4-disubstituted-1,2,3-triazoles (3a–c). Subsequent methylation of 1,4-disubstituted-1,2,3-triazoles (3a–c) yielded 1,3,4-trisubstituted-1,2,3-triazoliumiodide salts (4a–c) in appreciable yields. All the synthesized compounds were characterized by 1H and 13C NMR, ATR–IR spectroscopic techniques and elemental analyses. Additionally, the structure of 1-(4-chlorophenyl)-4-phenyl-1,2,3-triazole (3b) was confirmed by single crystal X-ray diffraction analysis. The catalytic activity of 4a–c in a catalytic system consisting of 1,3,4-trisubstituted-1,2,3-triazoliumiodide salt/palladium(II) acetate/base were investigated toward Suzuki–Miyaura and Heck–Mizoroki cross-coupling reactions. The Suzuki–Miyaura cross-coupling reactions were carried out under mild reaction conditions with good to excellent yields, whereas Heck–Mizoroki cross-coupling reactions were performed at elevated temperature with moderate yields. Further, in situ method skips the synthetic procedure of preparing the palladium(II) complexes and hence is more economical and less tedious.

Fully Conjugated Donor-Acceptor Block Copolymers for Organic Photovoltaics via Heck-Mizoroki Coupling.

The development of facile routes to prepare fully conjugated block copolymers (BCPs) from diverse monomers is an important goal for advancing robust bulk-heterojunction (BHJ) organic photovoltaics (OPVs). Herein we introduce a synthetic strategy for step-growth BCPs employing 1,2-bis(trialkylstannyl)ethene as one monomer, which, in addition to offering improved backbone planarity, directly yields a vinylene-terminated macromonomer suitable for Heck-Mizoroki coupling. The benefits of our strategy, which facilitates the preparation of functionalized macromonomers suitable for BCP synthesis, are demonstrated with a representative BCP based on a diketopyrrolopyrrole (DPP) copolymer coded pBDTTDPP as the donor block and a perylenediimide (PDI) copolymer coded as pPDIV as the acceptor block. Feed ratio optimization affords control over the macromonomer chain-end functionalities and allows for the selective formation of a tri-BCP consisting of pPDIV-b-pBDTTDPP-b-pPDIV, which is employed in a single-component BHJ OPV. Devices achieved a power conversion efficiency of 1.51% after thermal stress at 150 °C compared to 0.02% for a control device consisting of a comparable blend of pBDTTDPP and pPDIV. The difference in performance is ascribed to the morphological stability of the BHJ when using the BCP.

SA116Open Board

Cinchona-based chiral hyperbranched polymers (HBPs) were designed and successfully synthesized via the Mizoroki-Heck (MH) coupling reaction. AB2 and A2B-type chiral monomers were prepared from cinchona squaramide derivatives, where A (vinyl) reacted only with B (iodophenyl) under MH reaction conditions. The chiral HBPs obtained by the MH polymerization contained cinchona squaramide moieties and demonstrated excellent diastereoselectivity and enantioselectivity in asymmetric Michael addition reactions of methyl 2-oxocyclopentanecarboxylate and trans-β-nitrostyrene. These newly designed HBPs were structurally robust and could be reused for further reaction without losing their catalytic activity.

Synthesis of new Pro-PYE ligands as co-catalysts toward Pd-catalyzed Heck-Mizoroki cross coupling reactions.

The present research work describes the synthesis of five new ligands containing pyridinium amine, [H2L1][OTf]2–[H2L5][I]2 from two new precursors, [P3Et][I] and [P2Me][CF3SO3]. The structure elucidations of the compounds were confirmed by multinuclear NMR (1H, 13C), FT-IR and by single crystal XRD techniques. Theoretical DFT studies were carried out to get better insight into the electronic levels and structural features of all the molecules. These synthesized new Pro-PYE ligands [H2L1][OTf]2–[H2L5][I]2 were found to be significantly active as co-catalysts for Pd(CH3CO2)2 toward Heck–Mizoroki coupling reactions with wide substrate scope in the order of [H2L1][OTf]2 ≫ [H2L2][OTf]2 > [H2L3][OTf]2 > [H2L4][OTf]2 > [H2L5][I]2.

Salen–porphyrin-based conjugated microporous polymer supported Pd nanoparticles: highly efficient heterogeneous catalysts for aqueous C–C coupling reactions

Salen–porphyrin-based CMP supported Pd nanoparticles were employed as high-performance heterogeneous catalysts for aqueous Suzuki–Miyaura and Heck–Mizoroki coupling reactions.

A tailored polymeric cationic tag–anionic Pd(ii) complex as a catalyst for the low-leaching Heck–Mizoroki coupling in flow and in biomass-derived GVL

A new polystyrene-type resin loaded with pincer-type imidazolium ionic tag has been very effective in the immobilization of [PdCl4]2− palladium complex leading to a very low leaching of the metal during its use in flow.

Synthesis of chiral polyurethanes of cinchona alkaloids for the enantioselective synthesis in asymmetric catalysis

Chiral polyurethanes of cinchona alkaloid were synthesized via repetitive Mizoroki-Heck (MH) coupling reaction. The Pd-catalyzed polycondensation of cinchona urethane dimers and aromatic diiodides afforded the chiral polyurethanes. The chiral polyurethane bearing free OH group at the C6’ position of the quinoline ring in the cinchona alkaloid unit showed high catalytic activities and excellent enantioselectivities (up to 97% ee) in the Michael addition reactions.

Syntheses, characterization, solution behavior and catalytic activity of trans-[(guanidine)2PdX2] (X = Cl and OC(O)R; R = Me, Ph and tBu) in Heck–Mizoroki coupling reactions involving chloroarenes/methyl acrylate

Trans-[{(ArNH)2CNAr}2PdX2] (Ar = 2,5-Me2C6H3; X = Cl (1) and OC(O)R; R = Me (2), Ph (3), and tBu (4)) were isolated in high yields and characterized by elemental analysis, IR, and NMR (1H and 13C) spectroscopy. The molecular structures of the aforementioned complexes were determined by single crystal X-ray diffraction which revealed trans syn anti-anti (1·CHCl3), trans anti anti-syn (2·CHCl3 and 3·C7H8) and trans anti anti-anti (4) stereochemistry in solid state. Complexes 2·CHCl3, 3·C7H8 and 4 contain a pair of R11(8) rings stabilized by an intramolecular N–H⋯O hydrogen bond between the guanidine ligand and the carboxylate moiety. The influence of shape and size of the anion upon the stereochemistry of the complexes in the solid state and in solution are discussed. VT 1H NMR spectroscopic studies carried out on samples of 1 and 3 revealed the presence of a mixture of two rotamers in solution which arise due to the restricted CN(H)Ar single bond rotation of the guanidine ligand in both complexes. Complexes 1–4 were shown to be active catalysts even when used in 0.001 mol% in Heck–Mizoroki coupling reactions involving chlorobenzene and methyl acrylate. The scope of 1 in Heck–Mizoroki coupling reactions involving methyl acrylate and nine distinct chloroarenes were explored at 0.01 mol% which afforded the coupling products in 81−96% yields.

Pd salen complex@CPGO as a convenient, effective heterogeneous catalyst for Suzuki–Miyaura and Heck–Mizoroki cross-coupling reactions

A Pd(II) Schiff base complex supported on graphene oxide nanosheets (Pd(II) salen@CPGO) has been synthesized and characterized by FT-IR, ICP-AES, XRD, SEM/EDX and TEM. The synthesized nanocatalyst has been found to be an efficient heterogeneous catalyst for Suzuki–Miyaura and Heck–Mizoroki coupling reactions. Pd(II) salen@CPGO could be separated and recovered easily from the reaction mixture and recycled several times without a discernible decrease in its catalytic activity. The construction of a solid sheet-supported Pd catalyst would be expected to be a promising system to perform heterogeneous catalytic reactions.

Cinchona Squaramide-Based Chiral Polymers as Highly Efficient Catalysts in Asymmetric Michael Addition Reaction.

We have synthesized novel chiral polymers containing a cinchona-based squaramide in the main chain. We designed a novel cinchona squaramide dimer that contains two cinchona squaramide units connected by diamines. The olefinic double bonds in the cinchona squaramide dimer were used for Mizoroki–Heck (MH) polymerization with aromatic diiodides. The MH polymerization of the cinchona squaramide dimer and aromatic diiodide proceeded well to give the corresponding chiral polymers in good yields. The catalytic activity of the chiral polymers was investigated for asymmetric Michael addition reactions. The effect of the squaramide structure of the polymeric catalyst on the catalytic performance is discussed in detail. We have surveyed the influence of the chiral polymer structure on the catalytic activity and enantioselectivity of the asymmetric reaction. The asymmetric Michael addition of β-ketoesters to nitroolefins was successfully catalyzed by polymeric cinchona squaramide organocatalysts to obtain the corresponding Michael adducts in good yields with excellent enantio- and diastereoselectivities. The polymeric catalysts were insoluble in commonly used organic solvents and easily recovered from the reaction mixture and reused several times without the loss of catalytic activity.

NHC Pd(II) and Ag(I) Complexes: Synthesis, Structure, and Catalytic Activity in Three Types of C-C Coupling Reactions.

Four bis-benzimidazolium salts, 1,4-bis[1′-(N-R-benzimidazoliumyl)methyl]-2,3,5,6-tetramethylbenzene 2X– (L1H2·(PF6)2: R = ethyl, X = PF6; L2H2·Br2: R = picolyl, X = Br; L3H2·Br2: R = benzyl, X = Br; and L4H2·Br2: R = allyl, X = Br), and their three N-heterocyclic carbene (NHC) Pd(II) and Ag(I) complexes, L1Pd2Cl4 (1), L2Ag2Br2 (2), and L4(AgBr)2 (3), as well as one anionic complex L3H2·(Ag4Br8)0.5 (4), have been synthesized and characterized. Complex 1 adopts a funnel-like type of structure, complex 2 adopts a cyclic structure, and complex 3 is an open structure. In the crystal packing of 1–4, one-dimensional polymeric chains and two-dimensional supramolecular layers are formed via intermolecular weak interactions, including hydrogen bonds, π–π interactions, and C–H···π contacts. The catalytic activities of NHC Pd(II) complex 1 in three types of C–C coupling reactions (Suzuki–Miyaura, Heck–Mizoroki, and Sonogashira reactions) were studied. The results show that this catalytic system is efficient for these C–C coupling reactions.

Synthesis of chiral polyesters of cinchona alkaloid catalysts for enantioselective Michael addition of anthrone to nitroalkenes

Chiral polyesters of cinchona alkaloid derivatives were synthesized via repetitive Mizoroki-Heck (MH) coupling reaction. Under MH reaction conditions, 4-iodobenzoylquinine and 4-iodobenzoylcupreine were easily polymerized via self polycondensation to afford the corresponding chiral polyesters. The MH reaction conditions were also applied to the two-component polycondensation of cinchona ester dimer and aromatic diiodide to obtain the chiral polyesters. These cinchona-based chiral polyesters were successfully applied as polymeric organocatalysts in the asymmetric Michael addition reaction. The chiral polyesters bearing free OH groups at the C6′ position of the quinoline rings showed high catalytic activities (up to 97% isolated yield) and good enantioselectivities (up to 92% ee) in the Michael addition of anthrone to nitroalkenes. Furthermore, these polymeric catalysts were stable and could be recycled and reused several times.

A new poly(N–heterocyclic carbene Pd complex) immobilized on nano silica: An efficient and reusable catalyst for Suzuki–Miyaura, Sonogashira and Heck–Mizoroki C‒C coupling reactions

In the present study, the catalytic activity of a new poly (N‒heterocyclic carbene PdII complex) immobilized on silica nanoparticles, (PdII–NHCs)n@nSiO2 was studied in the Suzuki–Miyaura, Sonogashira and Heck–Mizoroki reactions of different aryl halides with phenylboronic acid, phenylacetylene and styrene, respectively. The (PdII–NHCs)n@nSiO2 was applied as a highly effecient heterogeneous catalyst for C‒C coupling reactions. The catalyst was characterized by FT–IR and UV–vis spectroscopic techniques, thermogravimetric analysis (TGA), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE–SEM) and inductively coupled plasma optical emission spectrometry (ICP–OES). Also, the catalytic activity did not deteriorate after eight run, and the catalyst can be separated and recovered easily by taking it out of the reaction solution.

Optimizing the Mizoroki–Heck reaction of cyclic allyl amines: Gram-scale synthesis of preclamol without protecting groups

Though a widely used metal-catalyzed cross-coupling process, the Mizoroki–Heck (MH) reaction can be a capricious transformation. This is particularly true for oxidation-prone alkene substrates containing ligating heteroatoms, as in the case of N-alkyl tetrahydropyridines, whose MH reactions have been underexplored due to the many side reactions that hamper the process. Since the products of tetrahydropyridine Heck reactions are direct precursors to potent pharmacophores, and therefore of commercial value, this is a significant drawback. We report here the results of our study designed to deliver an optimized, scalable MH procedure for N-alkyltetrahydropyridines and its exemplification in a gram-scale synthesis of the drug substance preclamol.

Organoselenium–palladium(ii) complex immobilized on functionalized magnetic nanoparticles as a promising retrievable nanocatalyst for the “phosphine-free” Heck–Mizoroki coupling reaction

An air- and moisture-stable organoselenium–palladium complex immobilized on silica-coated magnetic nanoparticles is designed, synthesized and applied as a practical and retrievable catalyst in the Heck–Mizoroki cross-coupling reaction.

Tunable Heck-Mizoroki Reaction of Dibromonaphthalene Diimide with Aryl Ethylenes: Design, Synthesis, and Characterization of Coplanar NDI-Based Conjugated Molecules.

Rational design of coplanar NDI-based conjugated molecules was achieved by covalently connecting naphthalene diimide (NDI) units with aryl (Ar) groups through vinylene (V) linkers via Heck-Mizoroki reaction. Two series of products, diolefination products (ArVNDIVAr) and hydroxylated and mono-olefination products (HONDIVAr), can be obtained, respectively, in moderate to excellent yields (45-90%) under controlled conditions, in which catalyst and base play the key roles. Density functional theory calculation discloses the outstanding planarity of the two types of products. Large bathochromic shifts are observed in both the absorbance and photoluminescence spectra of the HONDIVAr (144 and 229 nm) and ArVNDIVAr (180 and 242 nm) π-systems. Bathochromic shifts can be adjusted within the broad wavelength range by introducing 4'-substituents, either electron-withdrawing group (NO2) or electron-donating group (NMe2), in the phenyl group of aryl ethylenes. ArVNDIVArs show bigger bathochromic shifts than HONDIVArs.

Synthesis of Cinchona Alkaloid Sulfonamide Polymers as Enantioselective Catalysts for the Michael Addition Reaction of β-Ketoester and Nitrostyrene

Mizoroki–Heck (MH) polymerization of cinchonidine-based sulfonamide dimers produces polymers containing a chiral sulfonamide moiety in each repeat unit. Quinidine sulfonamides are known to have excellent catalytic activity in the asymmetric Michael addition reaction of β-ketoester and nitrostyrene. We found that cinchonidine sulfonamides used as bifunctional chiral catalysts showed even higher stereoselectivity in the same reaction. The polymers synthesized by MH polymerization also showed high levels of diastereo- and enantioselectivity (up to 99% enantiomeric excess) in the reaction. Owing to the insolubility of the polymeric catalysts, they were separated easily from the reaction mixture and reused several times without any loss of catalytic activity.

Catalysis of Cross-Coupling and Homocoupling Reactions of Aryl Halides Utilizing Ni(0), Ni(I), and Ni(II) Precursors; Ni(0) Compounds as the Probable Catalytic Species but Ni(I) Compounds as Intermediates and Products

Both Ni(0) and Ni(I) compounds are believed to exhibit cross-coupling catalytic properties under various conditions, and the compounds Ni(PPh3)4 and NiCl(PPh3)3 are compared as catalysts for representative Suzuki–Miyaura and Heck–Mizoroki cross-coupling reactions. The Ni(0) compound exhibits catalytic activities, for cross-coupling of chloro and bromoanisole with phenylboronic acid and of bromobenzene with styrene, yielding results which are comparable with those of many palladium-based catalysts, but our findings with NiCl(PPh3)3 are at this point unclear. It seems to convert to catalytically active Ni(0) species under Suzuki–Miyaura reaction conditions and is ineffective for Heck–Mizoroki cross-coupling. The paramagnetic Ni(I) compounds NiX(PPh3)3 (X = Cl, Br, I) are characterized for the first time by 1H NMR spectroscopy and are found to exhibit broad meta and para resonances at δ 9–11 and 3–4, respectively, and very broad ortho resonances at δ 4−6; these resonances are very useful for detecting Ni(I) ...

Thiophene Methanimine–Palladium Schiff Base Complex Anchored on Magnetic Nanoparticles: A Novel, Highly Efficient and Recoverable Nanocatalyst for Cross-Coupling Reactions in Mild and Aqueous Media

In this study, a novel thiophene methanimine–palladium Schiff base complex anchored on decorated γ-Fe2O3 with 2-aminoethyl dihydrogen phosphate (γ-Fe2O3/AEPH2-TC-Pd) was synthesized as a new magnetically separable nanocatalyst. Characterization of the new designed nanocatalyst was performed successfully using different techniques such as FT-IR, XRD, XPS, TEM, TGA, VSM, ICP and elemental analysis. This nanocatalyst presented a superb catalytic activity for Suzuki–Miyaura and Heck–Mizoroki cross-coupling reactions. The most important features of the prepared catalytic system which makes the current protocol more beneficial from both industrial and environmental viewpoints are its ease of recovery and reusability up to nine cycles without appreciable loss of the catalytic performance, as well as accomplishing the reactions under mild conditions in aqueous media which is a great challenge in some cross-coupling reactions.