芳烃酰基化后还原制备芳香醇的工艺进展

芳烃制备高附加值精细化学品芳香醇(9-芴甲醇),一直以来存在产物选择性低以及合成成本高等问题。基于此,本文主要综述了芳烃酰基化后还原合成芳香醇的工艺,包括第一步采用Friedel-Crafts酰基化反应、Vilsmeier-Haack反应、Reimer-Tiemann反应、Duff反应等过程将芳烃酰基化合成芳香醛/酮;第二步通过金属氢化物还原、催化加氢还原、活泼金属还原、Cannizarro反应、Meerwein-Ponndorf-Verley还原反应等过程将芳香醛/酮还原合成芳香醇。在总结和归纳各种工艺过程优缺点的基础上,提出了合理的芳香醇制备工艺,为9-芴甲醇产业化制备技术的开发提供帮助。     

TiO2晶面依赖的Ir-TiOx相互作用对Ir/TiO2催化剂巴豆醛选择性加氢性能的影响

α,β-不饱和醇是一类重要的精细化学品,主要通过α,β-不饱和醛选择性加氢获得.由于α,β-不饱和醛分子中含有共轭的C=C键和C=O键,且后者键能更大,在热力学和动力学上均不利于C=O键的选择性加氢生成α,β-不饱和醇.因此,提高α,β-不饱和醛中C=O的加氢选择性是催化领域中一项挑战性的课题.巴豆醛属于典型的α,β-不饱和醛,研究其选择性加氢生成巴豆醇具有广泛的代表意义;Ir负载在具有还原性载体(如TiO2)上时,表现出很好的C=O加氢选择性,因此,成为近年来的研究热点.由于暴露不同晶面的TiO2具有不同的形貌和电子结构,因此研究Ir-TiO2相互作用的晶面依赖性及其对巴豆醛选择性加氢反应的影响具有重要意义.本文以分别暴露{101}、{100}和{001}晶面的锐钛矿TiO2纳米晶为载体,制备了负载型Ir/TiO2催化剂,系统研究了催化剂经过不同的预处理过程(在不同温度下H2还原和O2再氧化)后对巴豆醛的气相选择性加氢的性能.利用高分辨透射电镜、原位X射线光电子能谱和原位漫反射红外光谱及氨程序升温脱附等技术研究发现,预处理条件显著改变了Ir-TiOx的相互作用,包括Ir金属的几何、电子性质及催化剂表面酸性.这种相互作用与TiO2的暴露晶面密切相关,从而改变了不同Ir/TiO2催化剂上不同加氢反应行为.研究结果表明,经300℃预还原的Ir/TiO2-{101}催化剂催化性能最好,在80℃下初始反应速率为166.1 μmol g-Ir-1 s-1,巴豆醇的生成转化频率为0.022 s-1.与其他催化剂相比,Ir/TiO2-{101}催化剂表面Ir0浓度最高,表面酸度适中,因此表现出最佳的催化性能.同时Ir-TiOx界面在反应中的协同作用,对H2和巴豆醛分子中C=O键的吸附和活化起到了关键作用.然而当催化剂经过400℃的H2预还原后,由于产生了强的金属-载体相互作用使得TiOx对Ir粒子进行了包裹从而导致Ir-TiOx界面缺失,因而催化剂催化巴豆醛加氢性能降低.本文为理解金属-载体相互作用对巴豆醛选择性加氢反应的影响提供了新的见解,并为设计高性能α,β-不饱和醛选择性加氢催化剂提供了理论依据.     

Br(o)nsted酸性离子液体在醛醇缩合反应中的应用

合成了一系列Br(o)nsted酸性离子液体并将其应用在醛醇缩合反应中.醛醇缩合产物由于极好的溶剂性质等被广泛用作溶剂和试剂.离子液体[BSmim][OTf]在甲醛和乙二醇缩合生成1,3-二氧五环的反应中表现出了极好的催化活性,甲醛转化率和主产物1,3-二氧五环选择性分别可以达到96.1％和92.4％.对影响离子液体催化性能的因素进行了探索,并对催化反应中的离子液体的用量、反应温度、反应时间以及反应物料比进行了考察.通过Hammett酸度函数法测定了所用到离子液体的酸性,结果表明离子液体酸性与其在缩合反应中的催化活性顺序完全一致,酸性越强催化性能越好.结合实验给出了离子液体[BSmim][OTf]催化甲醛和乙二醇缩合反应的可能的反应机理.该催化剂体系具有良好的催化性能,反应可以在较温和的条件下进行,实现了高活性和高选择性的目标,产物易分离,催化剂重复使用7次,其催化活性基本不变.并将该Br(o)nsted酸性离子液体进一步应用到其他醛(酮)醇缩合反应中.     

蒙脱土负载碘催化多组分合成咪唑衍生物

以苯偶酰(1)、苯甲醛(2a)、苯胺(3)和醋酸铵（4)为原料,蒙脱土负载碘和三乙烯二胺（DABCO）为催化剂,通过多组分法合成了6种1,2,4,5-四芳基-1,3-咪唑衍生物,其结构经¹H NMR和IR确证。对反应条件进行了优化。结果表明：在最优反应条件｛以10 mol%MMT/I₂为催化剂,10 mol%DABCO为碱,正丁醇为溶剂,原料配比r［n(1）：n(2a) ：n(3) ：n(4)］=1.0：2.0：2.0：8.0,于110 ℃反应16 h｝下,产率最高为91.5%。     

Brønsted酸性离子液体在醛醇缩合反应中的应用

合成了一系列Brønsted酸性离子液体并将其应用在醛醇缩合反应中.醛醇缩合产物由于极好的溶剂性质等被广泛用作溶剂和试剂.离子液体[BSmim][OTf]在甲醛和乙二醇缩合生成1,3-二氧五环的反应中表现出了极好的催化活性,甲醛转化率和主产物1,3-二氧五环选择性分别可以达到96.1%和92.4%.对影响离子液体催化性能的因素进行了探索,并对催化反应中的离子液体的用量、反应温度、反应时间以及反应物料比进行了考察.通过Hammett酸度函数法测定了所用到离子液体的酸性,结果表明离子液体酸性与其在缩合反应中的催化活性顺序完全一致,酸性越强催化性能越好.结合实验给出了离子液体[BSmim][OTf]催化甲醛和乙二醇缩合反应的可能的反应机理.该催化剂体系具有良好的催化性能,反应可以在较温和的条件下进行,实现了高活性和高选择性的目标,产物易分离,催化剂重复使用7次,其催化活性基本不变.并将该Brønsted酸性离子液体进一步应用到其他醛（酮）醇缩合反应中.     

Computational analysis for the determination of deleterious nsSNPs in human MTHFD1 gene

Single nucleotide polymorphisms (SNPs) are the most common genetic polymorphisms and play a major role in many inherited diseases. Methylenetetrahydrofolate dehydrogenase 1 (MTHFD1) is one of the enzymes involved in folate metabolism. In the present study, the functional and structural consequences of nsSNPs of human MTHFD1 gene was analyzed using various computational tools like SIFT, PolyPhen2, PANTHER, PROVEAN, SNAP2, nsSNPAnalyzer, PhD-SNP, SNPs&GO, I-Mutant, MuPro, ConSurf, InterPro, NCBI Conserved Domain Search tool, ModPred, SPARKS-X, RAMPAGE, FT Site and PyMol. Out of 327 nsSNPs form human MTHFD1 gene, total 45 SNPs were predicted as functionally most significant SNPs, among which 17 were highly conserved and functional, 17 were highly conserved and structural residues. Among 45 most significant SNPs, 15 were predicted to be involved in post translational modifications. The p.Gly165Arg may interfere in homodimer interface formation. The p.Asn439Lys and p.Asp445Asn may interfere in binding interactions of MTHFD1 protein with cesium cation and potassium. The two SNPs (p.Asp562Gly and p.Gly637Cys) might interfere in interactions of MTHFD1 with ligand.     

A Biofuel Cell Based on Biocatalytic Reactions of Glucose on Both Anode and Cathode Electrodes

Biofuel cells based on electrocatalytic oxidation of NADH and reduction of H₂O₂ have been prepared using carbon fiber electrodes functionalized with graphene nano‐flakes. The electrochemical oxidation of NADH was catalyzed by Meldola's blue (MB), while the reduction of H₂O₂ was catalyzed by hemin, both catalysts were adsorbed on the graphene flakes due to their π‐π staking. In the next set of experiments, the MB‐ and hemin‐electrodes were additionally modified with glucose dehydrogenase (GDH) and glucose oxidase (GOx), respectively. The enzyme catalyzed reactions in the presence of glucose, NAD⁺ and O₂ resulted in the production of NADH and H₂O₂ in situ. The produced NADH and H₂O₂ were oxidized and reduced, respectively, at the bioelectrocatalytic electrodes, thus producing voltage and current generated by the biofuel cell. The enzyme‐based biofuel cells operated in a human serum solution modelling an implantable device powered from the natural biofluid. Finally, two enzyme‐based biofuel cell connected in series and operating in the serum solution produced electrical power sufficient for activation of an electronic watch used as an example device.     

Electrochemical Study of 2,4‐Dinitrophenylhydrazine as Derivatization Reagent and Aldehydes at Carbon Glassy Electrode

A selective method based on derivatization with 2,4‐dinitrophenylhydrazine (DNPH) is described for the determination of several carbonyl compounds. The factors affecting the derivatization reaction of aldehyde and DNPH were investigated. The product of the derivatization reaction has been characterized by UV/Vis spectrophotometry, NMR, infrared spectroscopy and cyclic voltammetry. Then, an electrochemical study for the determination of aldehyde‐2.4‐dinitrophenylhydrazone was performed at glassy carbon electrode (GCE) using square wave voltammetry (SWV). After the optimization of experimental parameters, the limits of detection (at 3σ ) obtained for all aldehyde‐2,4‐DNPH were varied from 15.82 to 78.39 μmol L⁻¹ and relative standard deviations were between 1.8 and 4.5%. Finally, the proposed method was applied to determine the aldehydes concentration in drinking water and orange juice samples with satisfactory results.     

Solving the Puzzle of One‐Carbon Loss in Ripostatin Biosynthesis

Ripostatin is a promising antibiotic that inhibits RNA polymerase by binding to a novel binding site. In this study, the characterization of the biosynthetic gene cluster of ripostatin, which is a peculiar polyketide synthase (PKS) hybrid cluster encoding cis‐ and trans‐acyltransferase PKS genes, is reported. Moreover, an unprecedented mechanism for phenyl acetic acid formation and loading as a starter unit was discovered. This phenyl‐C2 unit is derived from phenylpyruvate (phenyl‐C3) and the mechanism described herein explains the mysterious loss of one carbon atom in ripostatin biosynthesis from the phenyl‐C3 precursor. Through in vitro reconstitution of the whole loading process, a pyruvate dehydrogenase like protein complex was revealed that performs thiamine pyrophosphate dependent decarboxylation of phenylpyruvate to form a phenylacetyl‐S ‐acyl carrier protein species, which is supplied to the subsequent biosynthetic assembly line for chain extension to finally yield ripostatin.