Catalyst In Toluene Research Articles

Polyheptenamer: A chemically recyclable polyolefin enabled by the low strain of seven‐membered cycloheptene

AbstractLow‐strain cyclic olefin monomers, including five‐membered, six‐membered, eight‐membered, and macrocyclic rings, have been recently exploited for the synthesis of depolymerizable polyolefins via ring‐opening metathesis polymerization (ROMP). Such polyolefins can undergo ring‐closing metathesis depolymerization (RCMD) to regenerate their original monomers. Nevertheless, the depolymerization behavior of polyolefins prepared by ROMP of seven‐membered cyclic olefins, an important class of low‐strain rings, still remains unexplored. In this study, we demonstrate the chemical recycling of polyheptenamers to cycloheptene under standard RCMD conditions. Highly efficient depolymerization of polyheptenamer was enabled by Grubbs' second‐generation catalyst in toluene. It was observed that the monomer yields increased when the depolymerization temperature increased and the starting polymer concentration was reduced. A near‐quantitative monomer regeneration (>96%) was achieved within 1 h under dilute conditions (20 mM of olefins) at 60°C. Moreover, polyheptenamer exhibited a decomposition temperature above 430°C, highlighting its potential as a new class of thermally stable and chemically recyclable polymer materials.

Meso-Meso and β-Meso Imine-Bridged Thien-2-yl Porphyrin Dyads: Synthesis, Spectral and Electrochemical Investigations

Imine-bridged meso-meso and β-meso unsymmetrical thien-2-yl porphyrin dyads were synthesized by condensation of meso- and β-formyl derivatives of 5,10,15,20-tetrakis(3-methylthien-2-yl)porphyrinato nickel (II), Ni3MeThP with 5-(5-Aminothien-2-yl)-10,15,20-triphenylporphyrinato nickel(II), Ni5AThPP in the presence of lanthanum(III)triflate catalyst in toluene at 120 °C for 8 h. The structural, photophysical, and redox properties were investigated by 1H NMR, UV/Vis spectral, and electrochemical analysis. The near coplanarity of the linker thien-2-yl group with the central porphyrin π-system, which can influence the electron delocalization of these molecules, is explained using electronic spectroscopy and cyclic voltammetry. The stronger electronic interaction between the two porphyrin units and the increased nonplanarity of the macrocycle brought about by the β-meso imine bridging is indicated by the larger shift of redox potentials in the dyad-2 as compared to the dyad-1 system. The results of the present investigation reveal that the two distinct porphyrin units in dyads interact via their near planar thien-2-yl linker.

Enhancing the catalytic performance of Ni based catalysts in toluene reforming at low temperature by structuring on SiC extrudates

Catalytic structuration on SiC extrudates improves the catalytic performance of Ni based catalysts in toluene reforming, and provides promising materials for hot gas cleaning in biomass gasification.

An Efficient 4-Step Synthesis of Favipiravir with Industrial Potential

An efficient, economical synthetic route is developed for the antiviral drug favipiravir using a four-steps instead of a six-step protocol. Starting with 6-bromo-3-hydroxypyrazine-2-carboxamide the method offers an overall 65% molar yield. The prime intermediate 3,6-difluoropyrazine-2-carbonitrile was synthesized by reacting 3,6-dichloropyrazine-2-carbonitrile with potassium fluoride using tetrabutyl-ammonium bromide (TBAB) as a phase transfer catalyst in toluene and DMSO medium at reflux temperature (120 ºC). A simple purification method from fluoro intermediate was developed by making dicyclohexylamine salt and a neutral compound using hydrogen peroxide. The prepared pure favipiravir is fully characterized using NMR Mass and IR techniques. Validated analytical HPLC methods assessed the purity of the drug. The quality of the drug synthesized in terms of assay and impurities is well within the ICH and pharmacopeia standards.

Synthesis of benzo[b][1,5]diazocin-6(5H)-one derivatives via the Cu-catalysed oxidative cyclization of 2-aryl-1H-indoles with 1,1-enediamines.

A novel protocol for the synthesis of highly functionalized benzo[b][1,5]diazocin-6(5H)-one derivatives (BDCOs, 4 and 5) from 2-aryl-1H-indoles and 1,1-enediamines was developed via a complex cascade of reactions including regioselective free radical oxidation, the 1,2-addition of imine, imine-enamine tautomerization, intramolecular cyclization, and ring expansion. The cascade reaction was enabled by refluxing a mixture of two substrates in the presence of di-tert-butyl peroxide (DTBP) as an oxidant and anhydrous CuI as a catalyst in toluene under argon protection. Consequently, a series of BDCOs (4 and 5) were synthesized with high regioselectivity in good yield. This protocol can be used for the synthesis of functionalized BDCOs via a one-pot oxidative annulation reaction rather than a multi-step reaction, which is suitable for both combinatorial and parallel syntheses of BDCOs.

Copper-Catalyzed Ligand-Controlled Selective Borocarbonylation of α-Substituted Styrenes Toward β-Boryl Aldehydes and Cyclopropyl Boronate Esters

Copper-Catalyzed Ligand-Controlled Selective Borocarbonylation of α-Substituted Styrenes Toward β-Boryl Aldehydes and Cyclopropyl Boronate Esters

Self-Supported Polymeric Ruthenium Complexes as Olefin Metathesis Catalysts in Synthesis of Heterocyclic Compounds

New ruthenium olefin metathesis catalysts containing N-heterocyclic carbene (NHC) connected by a linker tether to a benzylidene ligand were studied. Such obtained self-chelated Hoveyda–Grubbs type complexes existed in the form of an organometallic polymer but could still catalyze olefin metathesis after being dissolved in an organic solvent. Although these polymeric catalysts exhibited a slightly lower activity compared to structurally related nonpolymeric catalysts, they were successfully used in a number of ring-closing metathesis reactions leading to a variety of heterocyclic compounds, including biologically and pharmacologically related analogues of cathepsin K inhibitor and sildenafil (Viagra™). In the last case, a good solubility of a polymeric catalyst in toluene allowed the separation of the product from the catalyst via simple filtration.

Taylor‐vortex membrane reactor for continuous gas‐liquid reactions

AbstractA unique Taylor‐vortex membrane reactor (TVMR) design for continuous gas‐liquid reactions is presented in this work. The reactor consists of a cylindrical rotor inside a stationary concentric cylindrical vessel, and a flexible system of equispaced baffle rings surrounding the rotor. This restricts the annular cross section to a small gap between the baffles and the rotor, and divides the annulus into 18 mixing zones. The baffles support a 6 m long PFA tubular membrane that is woven around the rotor. At 4 mL/min inlet flow rate, the TVMR showed a plug‐flow behavior and outperformed the unbaffled reactor, having 5–12 times lower axial dispersion. The continuous aerobic oxidation of benzyl alcohol was performed for 7 h using the Pd(OAc)2/pyridine catalyst in toluene at 100 °C and 1.1 MPa oxygen pressure. A stable conversion of 30% was achieved with 85% benzaldehyde selectivity, and no pervaporation of organics into the gas phase.

Mechanism for initiation cation polymerization of p-methylstyrene in the presence of BF3∙HF catalyst in toluene at 1:4 ratio

Mechanism for initiation cation polymerization of p-methylstyrene in the presence of BF3∙HF catalyst in toluene at 1:4 ratio

FeCl3 as an efficient catalyst for the synthesis of styrylquinoxalin-2(1H)-ones

The synthesis of (E)-3-substituted styrylquinoxalin-2(1H)-ones was achieved by the reaction of 3-methylquinoxalinone and aromatic aldehydes using FeCl3 as a catalyst in toluene under microwave irradiation. The protocol is endowed with milder reaction conditions, high yields of product, and easy workup procedures.

Investigation of the microrheological properties of the branched polystyrene using 2-(2-bromoisobutyryloxy) ethyl methacrylate as the inimer

ABSTRACT A novel functional inimer 2-(2-bromoisobutyryloxy)ethyl methacrylate(BiBEM) both with the double bond and bromide was designed and synthesised. The branched polystyrene (PS) was prepared by the atom transfer radical polymerisation (ATRP), using BiBEM as inimer (initator) and CuBr complexed with bipyridine as catalysts in toluene at 80°C. The molecular weight and the branching degree of the polystyrene were analysed by using triple detection size-exclusion chromatography (TD-SEC) and the storage modulus in a wide and high-frequency range of polystyrene microrheological properties were studied by the diffusive wave spectroscopy (DWS). By adjusting the ratio of inimer to catalysts, a series of branched polystyrene polymers with different molecular weight and branching degree were obtained. The increase of the BiBEM concentration led to a higher degree of branching, while higher molecular weight and broader molecular weight distribution are accompanied. The branched polystyrene showed low storage modulus and lower chain entanglement compared to linear analogues.

Mechanism for initiation cation polymerization of p-metylstyrene in the presence of BF3∙HF catalyst in toluene at 1: 1: 3 ratio

Mechanism for initiation cation polymerization of p-metylstyrene in the presence of BF3∙HF catalyst in toluene at 1: 1: 3 ratio

Toward the Direct Synthesis of HDPE Powders for Powder Bed Fusion Based Additive Manufacturing

AbstractPowder bed fusion (PBF) suitable polyethylene particles are targeted by means of a direct synthesis, using a bisimino pyridine iron catalyst (BIP FeCl2) supported on microsized silica particles. An active support is generated by treating spray dried silica microparticles with a methyl aluminoxane activated BIP FeCl2 catalyst in toluene. Semibatch ethylene polymerization is mapped with respect to pressure, temperature, and reaction time to find optimal reaction parameters. The optimized synthesis leads to round polyethylene particles with a median size of ≈50 µm which have a sinter window of 8–15 °C and an unconfined yield stress (ffc) of 1.5 in a ring shear tester. The Young modulus of injection molded samples is in the range of 150–250 Pa with an elongation at break of about 30%. The powder flowability is improved by coating with nanosilica powder to an ffc of 3.8. Additivitation with carbon black allows to laser sinter the powder to solid parts in a small scale adapted setup for selective laser sintering (PBF/laser beam (LB)/P). Severe caking is preventing the preparation of CAD model conform parts. Commercial HDPE powder for PBF is additivated the same way to give substantially solid built parts, but with similar caking.

One‐Pot Synthesis of α‐Diazo‐γ,δ‐unsaturated Esters as Versatile Building Blocks for Functionalized Dienes, Cyclopentenes, and 5,7‐Fused Bicycles

AbstractThe synthesis of novel allylic α‐diazo carbonyl compounds was achieved through a one‐pot strategy involving base‐catalyzed allylation of 1,3‐dicarbonyls with readily available allylic bromides followed by the deacylative diazo transfer reaction. Besides the broad substrate scope related to this method, other relevant features include the use of simple and inexpensive reagents, non‐toxic solvents and mild reaction conditions. The synthetic utility of these α‐diazo‐γ,δ‐unsaturated esters was further demonstrated through rhodium‐catalyzed transformations, where the type of product formed is dependent on both the substrate and catalyst employed. Thus, treating α‐diazo‐γ,δ‐unsaturated esters with catalytic Rh2(pfb)4 in acetonitrile under reflux resulted in a diastereoselective β‐hydride migration to give 2Z,4E‐dienes in good yields. On the other hand, the combination of Rh2(OAc)4 as the catalyst in toluene under reflux for 10 min led the aryl‐substituted diazo compounds to a regioselective intramolecular Buchner reaction to furnish 5,7‐fused bicyclic tetraenes in high yields, while the alkyl‐substituted analogues undergo intramolecular C–H insertion to give functionalized cyclopentenes of anti‐configuration.

Front Cover Picture: Palladium‐Catalyzed Regioselective C−H Arylation of 4‐Azaindazole at C3, C5 and C7 Positions (Adv. Synth. Catal. 16/2021)

The front cover picture, designed by El Kazzouli and co-workers, illustrates the site-selective C5 and C7 palladium-catalyzed C-H arylations of 4-azaindazole N-oxide. The 1,10-phenanthroline as ligand and Pd(OAc)2 as catalyst in toluene promoted the activation of C5 position, while the triphenyl phosphine as ligand and PdCl2 as catalyst in DMA directed the arylation at C7 position. This new method allows the synthesis of C5, C7-diarylated 4-azaindazole N-oxides as well as the C3, C5, C7-triarylated 4-azaindazoles. Details can be found in the Communication by El Kazzouli, Suzenet, Guillaumet and co-workers (S. Faarasse, S. El Kazzouli, O. Bourzikat, S. Bourg, S. Aci-Sèche, P. Bonnet, F. Suzenet, G. Guillaumet Adv. Synth. Catal. 2021, 363, 3937–3945; DOI: 10.1002/adsc.202001421).

Mechanism for initiation cation polymerization of p-metylstyrene in the presence of BF3∙HF catalyst in toluene at 1: 1: 2 ratio

Mechanism for initiation cation polymerization of p-metylstyrene in the presence of BF3∙HF catalyst in toluene at 1: 1: 2 ratio

Palladium‐Catalyzed Regioselective C−H Arylation of 4‐Azaindazole at C3, C5 and C7 Positions

AbstractDirect and site‐selective C5 and C7 palladium‐catalyzed C−H arylations of 4‐azaindazole N‐oxide have been achieved. A bidentate ligand and Pd(OAc)2 catalyst in toluene promoted the activation of C5 position, while a phosphine ligand and PdCl2 catalyst in DMA directed the arylation at C7 position. Using this new method, the synthesis of C5, C7‐diarylated 4‐azaindazole N‐oxides as well as the C3, C5, C7‐triarylated 4‐azaindazoles was achieved towards future medicinal compounds development.magnified image

Synthesis and Anti-Proliferative Assessment of Triazolo-Thiadiazepine and Triazolo-Thiadiazine Scaffolds.

A series of triazolo-thiadiazepines 4a–k were synthesized with excellent yields using dehydrated PTSA as a catalyst in toluene. Two triazolo-thiadiazines were obtained; 8a was formed directly by reflux in ethanol, whereas, PTSA promoted the formation of 8b. The molecular structure of the formed triazolo-thiadiazepines is identical to the imine-form 4a–k and not the enamine-tautomer 6a–k. The structures of the newly synthesized triazolo-thiadiazepines 4a–k and triazolo-thiadiazines 8a–b were elucidated using NMR (1H, and 13C), 2D NMR, HRMS, and X-ray single crystal. Furthermore, 4a was deduced using X-ray single crystal diffraction analysis. These new thiadiazepine hits represent an optimized series of previously synthesized indole-triazole derivatives for the inhibition of EGFR. The cytotoxicity activity against two cancer cell lines including human liver cancer (HEPG-2) and breast cancer (MCF-7) was promising, with IC50 between 12.9 to 44.6 µg/mL and 14.7 to 48.7 µg/mL for the tested cancer cell lines respectively, compared to doxorubicin (IC50 4.0 µg/mL). Docking studies revealed that the thiadiazepine scaffold presented a suitable anchor, allowing good interaction of the various binding groups with the enzyme binding regions and sub-pockets.

Synthesis of 1-chlorocyclohexenyl-2-aminobenzenes: A new class of cyclic vinylamines by the Buchwald-Hartwig reaction

Reaction of 1-bromo-2-chlorocyclohexene with ten aryl amines, sodium tert-butoxide and Pd[2-(furan-2′-yl)-1H-benzo[d]imidazole]2Cl2 as catalyst in toluene under sealed pressure tube conditions at 80 °C gave the novel 1-chlorocyclohexenyl-2-aminobenzenes, in greater than 85% yields. The compounds were characterized by spectroscopic techniques.

NHC Nickel Catalyzed Hiyama‐ and Negishi‐Type Cross‐Coupling of Aryl Fluorides and Investigations on the Stability of Nickel(II) Fluoroaryl Alkyl Complexes

The reactivity of [Ni(iPr2Im)4(µ‐COD)] 1 (iPr2Im = 1,3‐diisopropyl‐imidazolin‐2‐ylidene, COD = 1,4‐cyclooctadiene) in Hiyama‐ and Negishi‐type cross‐coupling reactions as well as the synthesis of several novel nickel fluoroaryl alkyl complexes is reported. Hiyama coupling of 1.1 equiv. perfluoroaromatics and 1 equiv. PhSi(OR)3 (R = Me, Et) with 5 mol‐% of 1 as catalyst leads to the C–C coupling product ArF–Ph in good to fair yields. In presence of the additive NMe4F alkoxy transfer from PhSi(OR)3 to the perfluoroarene occurs to yield ArF–OR and PhSiF(OR)2. Negishi cross‐coupling between C6F6 or C7F8 (1 equiv.), diorganozinc reagents [ZnR2] (R = Me, Et) (2.1 equiv.) and 5 mol‐% 1 as the catalyst in toluene at 115 °C leads to ArF–R only in traces. However, NMR experiments revealed that nickel alkyl complexes are readily formed from the reaction of trans‐[Ni(iPr2Im)2(F)(ArF)] with [ZnR2] (R = Me, Et). In course of these investigations, a series of novel nickel alkyl complexes trans‐[Ni(iPr2Im)2(R)(ArF)] (R = Me, ArF = C6F5 2, C7F7 3, C12F9 4; R = Et, ArF = C6F5 5, C7F7 6, C12F9 7) have been synthesized in stoichiometric reactions starting from trans‐[Ni(iPr2Im)2(F)(ArF)] (ArF = C6F5, C7F7, C12F9) and [ZnR2] (R = Me, Et) in thf at –78 °C. As these nickel alkyl complexes 2–7 are stable at room temperature in solution for several days with respect to reductive elimination, their thermal stability was investigated. Heating trans‐[Ni(iPr2Im)2(Me)(C6F5)] 2 for 24 hours at 100 °C leads to 91 % unreacted complex 2 and only traces of reductive elimination product, i.e. C6F5Me, are formed. Furthermore, the nickel ethyl complex trans‐[Ni(iPr2Im)2(Et)(C6F5)] 5 is also very stable, even with respect to β‐hydride elimination. After heating this complex to 100 °C for 24 hours there is still 26 % unreacted 5 left.