Benzylation of arenes and heteroarenes catalyzed by HfCl_4/HfO_2

A highly efficient benzylation of arenes and heteroarenes catalyzed by HfCl4/HfO2 has been developed. Broad scope of benzylation reagents have been used in this process with high yields under mild condition. Additionally, the HfO2 can be re-used after the reaction. ？2009 Xin Qin Gao. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Synthesis of Pharmaceutical Intermediates by Toluene Benzylation over Heteropoly Acids on Different Support

Selective formation of pharmaceutical intermediates like diphenylmethane, dimethyldiphenylmethane, benzyl toluene and benzoic acid by liquid phase, toluene benzylation with benzyl chloride as a benzylating agent, was systematically studied over plane clay （K-10, montmorillonite）, plane H-Beta, plane MFI structured titanosilicate （TS-1） and heteropoly acids [HPA, namely dodecatungstophosphoric acid [H3PO4.12WOa-xH2O] （TPA）, dodeca-molybdo phosphoric acid ammonium salt hydrate [H12Mo12N3040P＋aq] （DMAA）, sodium tungstate hydrated purified [Na12WO4.2H2O] （STH）] supported on clay, H-beta and TS-1. The 20%TPA/Clay, 30%TPA/H-Beta and 30%TPA/TS-1, were observed to be the best catalyst samples over plane clay, plane H-Beta and plane TS-1. The catalyst samples are compared with respect to benzyl chloride conversion and selectivities for diphenylmethane, dimethyl-diphenylmethane, benzyl toluene and benzoic acid. The reaction follows the pseudo-first order rate power law model. The apparent rate constants are calculated and compared with the reported ones.

Selective debenzylation of benzyl esters by silica-supported sodium hydrogen sulphate

A new debenzylation of benzyl esters by silica-supported sodium hydrogen sulfate is described. The debenzylation could be achieved selectively and efficiently in good to excellent yields without affecting sensitive functional groups such as nitro, unsaturated bonds, and ethyl ester.

Modification of pillared MFI zeolite nanosheets by nitridation with tailored activity in benzylation of mesitylene and benzyl alcohol

The modification of pillared MFI zeolites was performed by nitridation of silica pillared MFI zeolite nanosheets under NH3 atmosphere with different time. The resultant zeolites were characterized by a complementary combination of X-ray power diffraction(XRD), scanning electron microscopy(SEM),transmission electron microscopy(TEM), pyridine-IR spectroscopy and N2 adsorption–desorption isotherms. The analyses showed that the nitridation didn’t destroy the crystallinity and specific surface area of zeolites, and the acidity of zeolites can be tailored by tuning the time of nitridation, resulting in the different concentration ratios of Br?nsted-to-Lewis(B/L) acid sites. Moreover, the nitrided zeolites exhibited high selectivity to 2-benzyl-1,3,5-trimethylbenzene than parent silica pillared MFI zeolite nanosheets in benzylation of mesitylene with benzyl alcohol. A balance between Br?nsted acid sites and Lewis acid sites can inhibit the self-etherification of benzyl alcohol and enhance the selectivity of alkylated product. These experimental data implied that nitridation was an effective method to modulate the acidity of zeolites and the synergy between Br?nsted acid sites and Lewis acid sites was a decisive factor to determine the selectivity.

Benzylation of Aromatic Compounds with Benzyl Chloride Catalyzed by Nafion/SiO_2 Nanocomposite Catalyst

In the presence of Nafion/SiO2 nanocomposite catalyst, the benzylation of aromatic compounds with benzyl chloride proceeded to afford diphenylmethane derivatives in high yields. The catalyst showed high catalytic activity not only for electron-rich aromatic compounds, but also for electron-poor aromatic compounds. Under identical conditions, the self-benzylation of benzyl chloride, and dibenzylation and/or multi-benzylation of aromatic compounds were negligible.

BF₃.OEt₂-Mediated Benzylation of Arenes and Heteroarenes with Benzyl Ether Derivatives

An efficient BF3.OEt2-promoted benzylation of arenes and heteroarenes with various benzyl ether derivatives has been developed. This method provided alternative access to valuable diarylmethane in good yields under mild conditions via an easy work-up procedure.

Direct benzylation reactions from benzyl halides enabled by transition-metal-free photocatalysis

An SN2-based photochemical strategy using dithiocarbamate anion as catalyst was developed for the activation of benzyl halides,which are extremely challenging to be applied as radical precursors in visible light photocatalysis.With this transition-metal-free and oxidant-free protocol,the benzylation(or cyanomethylation)of various heterocycles including quinoxalin-2(1H)-ones,coumarin,2-phenyl-2H-indazole,1-methyl-5-phenylpyrazin-2(1H)-one,1-(fluoromethyl)cinnolin-4(1H)-one,and 2,4-dibenzyl-1,2,4-triazine-3,5(2H,4H)-dione could be realized(46 examples,up to 98%yield).Importantly,some biologically relevant 3-benzylquinoxalin-2(1H)-ones were also be synthesized under mild conditions.

Catalytic Benzylation Reactions: From C-H Bond Activation to C-N Bond Activation

Transition-metal mediated activation of inert chemical bonds is an ongoing topic in homogeneous catalysis.In view of the abundance and accessibility of alkylarenes and benzylamines,the use of them as benzyl source in catalytic benzylation reactions via benzylic C-H and C-N bond activation is highly desirable.Indeed,compared with the traditional approaches with benzyl halide as the substrates,benzylation reactions via C-H and C-N bond cleavage provide more efficient,atom-economic strategies to access myriads of synthetically important molecules.In this account,our group's efforts on catalytic benzylation reactions via directed C-H activation,nondirected C-H activation and C-N bond activation are summarized.

Chemoselective Benzylation and Allylation of 4-Nitrobenzaldehyde Promoted by Phase Transfer Catalyst and Metal in Aqueous Media

The benzylation and allylation of 4-nitrobenzaldehyde (1) could be controlled chemoselectively by using different phase transfer catalyst (FTC) and different metal catalysts. And then, benzylation and allylation of 1 with various organic halides has been realized in high yields in aqueous media.

PHASE TRANSFER CATALYSED BENZYLATION OF CHITIN

Polysaceharide is a polyhydroxyl maeromolecular compound. Owing to the influence of the intermolecular and intramolecular hydrogenbonds and difficulty in achieving reaction in solution, it is difficult to obtain products of its complete or selective substitution in the research of polysaccharide modification or structure. The

Organocatalytic difluorobenzylation of 1,2-diketones via mild cleavage of carbon-carbon bonds

α-Aryl-α,α-difluoroacetophenones(DFAPs)are developed as a new class of difluorobenzylation reagents that can be facilely prepared from readily available and cheap starting materials.In situ carbon-carbon bond cleavage of electron-deficient DFAPs gives difluorobenzyl carbanions that undergo base-catalyzed nucleophilic addition to isatins.

Functional characterization and key residues engineering of a regiopromiscuity O-methyltransferase involved in benzylisoquinoline alkaloid biosynthesis in Nelumbo nucifera

Lotus(Nelumbo nucifera),an ancient aquatic plant,possesses a unique pharmacological activity that is primarily contributed by benzylisoquinoline alkaloids(BIAs).However,only few genes and enzymes involved in BIA biosynthesis in N.nucifera have been isolated and characterized.In the present study we identified the regiopromiscuity of an O-methyltransferase,designated NnOMT6,isolated from N.nucifera;NnOMT6 was found to catalyze the methylation of monobenzylisoquinoline 6-O/7-O,aporphine skeleton 6-O,phenylpropanoid 3-O,and protoberberine 2-O.We further probed the key residues affecting NnOMT6 activity via molecular docking and molecular dynamics simulation.Verification using site-directed mutagenesis revealed that residues D316,N130,L135,N176A,D269,and E328 were critical for BIA O-methyltransferase activities;furthermore,N323A,a mutant of NnOMT6,demonstrated a substantial increase in catalytic efficiency for BIAs and a broader acceptor scope compared with wild-type NnOMT6.To the best of our knowledge,this is the first study to report the O-methyltransferase activity of an aporphine skeleton without benzyl moiety substitutions in N.nucifera.The study findings provide biocatalysts for the semisynthesis of related medical compounds and give insights into protein engineering to strengthen O-methyltransferase activity in plants.

Different efficiency toward the biomimetic aerobic oxidation of benzyl alcohol in microchannel and bubble column reactors: Hydrodynamic characteristics and gas–liquid mass transfer

The selective aerobic oxidation of benzyl alcohol to benzaldehyde has attracted considerable attention because benzaldehyde is a high value-added product. The rate of this typical gas–liquid reaction is significantly affected by mass transfer. In this study, CoTPP-mediated(CoTPP: cobalt(II) mesotetraphenylporphyrin) selective benzyl alcohol oxidation with oxygen was conducted in a membrane microchannel(MMC) reactor and a bubble column(BC) reactor, respectively. We observed that 83% benzyl alcohol was converted within 6.5 min in the MMC reactor, but only less than 10% benzyl alcohol was converted in the BC reactor. Hydrodynamic characteristics and gas–liquid mass transfer performances were compared for the MMC and BC reactors. The MMC reactor was assumed to be a plug flow reactor,and the dimensionless variance was 0.29. Compared to the BC reactor, the gas–liquid mass transfer was intensified significantly in MMC reactor. It could be ascribed to the high gas holdup(2.9 times higher than that of BC reactor), liquid film mass transfer coefficient(8.2 times higher than that of BC reactor), and mass transfer coefficient per unit interfacial area(3.8 times higher than that of BC reactor). Moreover,the Hatta number for the MMC reactor reached up to 0.61, which was about 15 times higher than that of the BC reactor. The computational fluid dynamics calculations for mass fractions in both liquid and gas phases were consistent with the experimental data.

Biotransformation of Gastrodin by Mucor spinosus

Microbial transformation of gastrodin by Mucor spinosus strain 3.3450, resulted in a product with a transformation rate close to 100 per cent. This product was identified as p-hydroxy benzyl alcohol on the basis of its 1H, 13C NMR and EI-MS spectral data. It could be inferred that the enzyme responsible for the biotransforma-tion reaction was a kind of extracellular and constitutive enzyme since the transformation reaction of the substrate could be carried out in cell free extracts of the fermentation broth of the Mucor spinosus.

Chemical Constituents of Thalictrum delavayi

Two new compounds, 5-hydro-N-methylcorydalidine (1) and 1-(4-methoxybenzyl)-2-N-methyl-6-hydroxyl-5, 7-dimethoxy-isoquinoline (2), together with seven known ones (3-9) were isolated from the chloroform extract of the herb Thalictrum delavayi Franch., among which compound 7 was firstly obtained from the genus Thalictrum. Their structures were elucidated on the basis of spectroscopic evidence including HMQC and HMBC experiments.

气相色谱法测定多烯磷脂酰胆碱注射液中的苯甲醇

建立了多烯磷脂酰胆碱注射液中苯甲醇含量的测定方法。采用毛细管气相色谱法，以环己醇作为内标物，使用AT．SE-54毛细管色谱柱，程序升温，N2为载气，不分流进样模式，氢火焰离子化检测器（FID）检测。结果表明苯甲醇在0．01～20．0g／L范围内峰面积与内标峰面积的比值与其质量浓度呈良好的线性关系（r=0．9997），平均加样回收率为99．7％，相对标准偏差（RSD）为1．07％。该方法简便，准确，重现性好，精密度高，适用于多烯磷脂酰胆碱注射液中苯甲醇含量的测定，为同类药物的质量控制提供了实验依据。

Effect of Crystalline Structure of Wood on Liquefaction

By means of X ray and gas chromatography analysis, the crystalline structure of untreated wood , alkali treated wood and benzylated wood and their liquefaction in toluene and tetrahydrofufan with HCl as a catalyst were studied .The upper solution of benzylated wood was also studied by GC MS analysis. It proved that the introduction of bulky benzyl group in wood significantly changed the crystalline structure of wood ,enlarging the free volume which facilitated the penetration of solvent into the matrix of treated wood, thus tremendously enhancing thesolubility in solvent,compared to untreated wood and alkali treated wood. The percentage of residue decreased and the combined solvent increased with the increase of weight gain revealed that the liquefaction process became easy. Furthermore, the factors that influenced the liquefaction of benzylated wood were investigated. It showed that the liquefaction performance was improved with the increase of liquefaction time and the amount of catalyst when toluene was used as a solvent, especially in the presence of THF as solvent, there existed the optimum liquefaction time and the amount of catalyst .

Synthesis and Characterization of Side-Chain Liquid Crystalline Polysiloxanes

Side chain liquid crystalline golysiloxanes conta ing biphenyl and benzyl ether mesogen were synthesized by the hydrosilation of poly(methylhydrcsiloxane) with 4-(4-allyloxybenzytoxy)-4'- methoxybiphenyl(M_1),4-(4-allyloxybenzyloxy)-4'-ethoxybiphenyl(M_2),4-(4-allyloxybenzyloxy)-4'- propoxybiphenyl(M_3),4-(4-allyloxybenzyloxy)-4'-butoxybiphenyl(M_4),4-(4-allyloxybenzyloxy)-4'- pentyloxybiphenyl(M_5).The phase behavior of monomeric and polymeric liquid crystals was chararcterized by differential scanning calorimetry and optical polarization microscopy.Both the monomeric and polymeric liquid crystals exhibit liquid crystal behaviors.

Ag-Ni alloy nanoparticles for electrocatalytic reduction of benzyl chloride

Ag-based nanocatalysts exhibit good catalytic activity for the electrochemical reduction of organic halides. Ag-Ni alloy nanoparticles（NPs） were facilely prepared by chemical reduction, and the as-prepared nanocatalysts were characterized by X-ray diffraction, ultraviolet-visible spectroscopy, transmission electron microscopy and energy-dispersive X-ray spectroscopy. The electrocatalytic activity of Ag-Ni NPs for benzyl chloride reduction was studied in organic medium using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. The results show that the addition of Ni element can obviously decrease the size of Ag-Ni NPs, shift the reduction peak potential（φp） of benzyl chloride positively, and increase the catalytic activity of Ag-Ni NPs. However, when the Ni content reaches a certain value, the catalytic activity of Ag-Ni NPs decreases. Meanwhile, the synergistic catalytic effect of Ag-Ni NPs was also discussed.

An Unusual Reductive Ring-opening Reaction of Phthalimide with Sodium Hydride in DMF

An unusual reductive ring-opening reaction of phthalimide with sodium hydride in anhydrous DMF was observed for the first time. The presumed mechanism was described in detail.