Enzymatic synthesis of gallic acid esters

Esters of gallic acid were synthesized by enzymatic means using tannase fromAspergillus niger. Alcohols ranging from C₁ through C₁₂ and diols from C₃ through C₆ were tested and found to form esters in the presence of the enzyme.     

Investigation of racemisation in peptide synthesis within a micro reactor

We demonstrate that peptides derived from alpha-amino acids may be prepared in a micro reactor. The peptides were prepared in 20 min with quantitative conversion, compared to batch reactions which require prolonged reaction times. We illustrate that by using dilute reagent concentrations and short reaction times, less racemisation is observed in micro reactions than in bulk reactions.     

The preparation and reaction of enolates within micro reactors

Over the past 5 years, interest in the miniaturisation of chemical synthesis has grown rapidly, however in order to facilitate transfer of the technology from its current position as a research tool to industrial applications, a core understanding of the challenges associated with transferring reactions from the macro to the micro domain is required. This paper therefore aims to broach this problem by investigating the application of micro reactors to a range of commonly employed synthetic reactions including acylation, aldol, alkylation, 1,4-conjugate addition (Michael addition) and the Knoevenagel condensation. Comparison of the results obtained with traditional batch techniques enable us to highlight some of the advantages associated with micro reaction technology.     

含氮合成气在三相淤浆床-固定床中直接合成二甲醚

在三相淤浆床－固定床反应装置中,研究含氮合成气直接合成二甲醚。使用双功能混合催化剂,粒度为0.15 mm～0.18 mm。在220 ℃～260 ℃、3.0 MPa～7.0 MPa、空速1 000 mL·g-1·h-1时考察了温度、压力及两种反应器中催化剂的装填比例对CO转化率及二甲醚选择性的影响。结果表明,一氧化碳转化率随反应压力的增加而提高,随着温度升高二甲醚的选择性变化不大,CO转化率的升高较明显,因此在催化剂活性适宜的温度范围内,该反应装置可以采用较高的反应温度。当260 ℃、7.0 MPa、三相床与固定床中催化剂比例为1∶1时,CO的转化率可达84.5％,二甲醚的选择性为78.7％。淤浆床－固定床反应装置具有操作稳定性好、CO转化率高的优点。催化剂在该装置中反应370 h活性没有明显下降。     

Highly enantioselective hydrogenation of 3,5-diketo esters: a formal synthesis of tetrahydrolipstatin

Compound 4, obtained via a sequence of two consecutive alkylations of methyl 3,5-dioxohexanoate (5), was transformed into the enantiomerically pure lactone (3S,4S,6R)-2 being the precursor of tetrahydrolipstatin (1). The reaction sequence involves asymmetric catalytic hydrogenation of 4 as a crucial step.     

Cathodic synthesis of esters of 1,1,2,2-cycloalkanetetracarboxylic acids derived from 1,1,2,2-ethane- or ethylenecarboxylate esters

The cathodic electrolysis of esters of 1,1,2,2-ethane- or ethylenetetracarboxylic acids in the presence of dihaloalkanes leads to esters of 1,1,2,2-cycloalkanetetracarboxylic acids.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 217–220, January, 1992.     

Conversion enhancement of tubular fixed-bed reactor for Fischer-Tropsch synthesis using static mixer

Recently,Fischer-Tropsch synthesis(FTS) has become an interesting technology because of its potential role in producing biofuels via Biomassto-Liquids(BTL) processes.In Fischer-Tropsch(FT) section,biomass-derived syngas,mainly composed of a mixture of carbon monoxide(CO) and hydrogen(H2),is converted into various forms of hydrocarbon products over a catalyst at specified temperature and pressure.Fixed-bed reactors are typically used for these processes as conventional FT reactors.The fixed-bed or packed-bed type reactor has its drawbacks,which are heat transfer limitation,i.e.a hot spot problem involved highly exothermic characteristics of FT reaction,and mass transfer limitation due to the condensation of liquid hydrocarbon products occurred on catalyst surface.This work is initiated to develop a new chemical reactor design in which a better distribution of gaseous reactants and hydrocarbon products could be achieved,and led to higher throughput and conversion.The main goal of the research is the enhancement of a fixed-bed reactor,focusing on the application of KenicsTM static mixer insertion in the tubular packed-bed reactor.Two FTS experiments were carried out using two reactors i.e.,with and without static mixer insertion within catalytic beds.The modeled syngas used was a mixed gas composed of H2/CO in 2:1 molar ratio that was fed at the rate of 30mL(STP)min1(GHSV≈136mL g1 cat h1) into the fixed Ru supported aluminum catalyst bed of weight 13.3g.The reaction was carried out at 180℃ and atmospheric pressure continuously for 36h for both experiments.Both transient and steady-state conversions(in terms of time on stream) were reported.The results revealed that the steady-state CO conversion for the case using the static mixer was approximately 3.5 times higher than that of the case without static mixer.In both cases,the values of chain growth probability of hydrocarbon products(α) for Fischer-Tropsch synthesis were 0.92 and 0.89 for the case with and without static mixer,respectively.     

On-chip separation of peptides prepared within a micro reactor

We have demonstrated that peptides may be electrophoretically separated from unreacted reagents within an integrated micro reactor.     

Optimum catalytic reactor design for methanol synthesis with TEC MRF-Z? reactor

The concept of Multi-stage indirect cooling and Radial Flow (MRF) is ideal for designing a catalytic reactor in which an exothermic equilibrium reaction takes place. The reaction is controlled to go on along the path of the maximum reaction rate in the catalyst bed where synthesis gas flows radially in the catalyst beds from the outer side to an inner center pipe across boiler (cooling) tubes to recover the reaction heat as qualitative steam. The MRF concept has already been proven in a commercial scale methanol plant and is unique not only for saving energy but also for considerable scale-up for which the enhanced design, MRF-Z^®, provides. MRF-Z^® is now offered for single train 5,000 t/d reactors used in so-called jumbo methanol plants.     

Facile one-pot synthesis of functionalized organophosphonate esters via ketone insertion into bulky arylphosphites

The reaction of phosphorus trichloride with 2,6-diisopropyl phenol in the presence of LiCl under reflux conditions for 24 h produces a mixture of (ArO)PCl₂ and (ArO)₂PCl (Ar = 2,6-iPr₂C₆H₃). The hydrolysis of the aryloxy compounds in acetone/H₂O results in the formation of two novel phosphonate ester derivatives [(ArO)P(O)(OH)(CMe₂OH)] (1) and [(ArO)₂P(O)(CMe₂OH)] (2), respectively in a moderate yield. The title compounds have presumably formed via acetone insertion to the P-H bonds of (ArO)P(O)(H)(OH) and (ArO)₂P(O)(H), respectively, in the presence of HCl produced during the hydrolysis. Compounds 1 and 2 have been characterized by elemental analysis, and ESI-mass, Infrared and NMR spectroscopic techniques. Further, solid state structures of 1 and 2 have been established by single crystals X-ray diffraction studies.     

The regioselective preparation of 1,3-diketones within a micro reactor

We demonstrate a simple method for the regioselective preparation of 1,3-diketones within a micro reactor from silyl enol ethers where the products are free from both competing O-acylation and diacylation products.     

Microwave-assisted solution phase synthesis of dihydropyrimidine C5 amides and esters

Multifunctionalized dihydropyrimidine-5-carboxylic amides and esters are generated in a multistep sequence integrating a variety of enabling and high throughput technologies such as automated or parallel microwave synthesis, the use of polymer-supported reagents, fluorous synthesis and purification strategies, and a continuous flow hydrogenation system. The key dihydropyrimidine-5-carboxylic acid intermediates are obtained in two steps by Biginelli multicomponent condensation of benzyl or allyl β-ketoesters with aldehydes and urea/thioureas, followed by suitable benzyl or allyl deprotection strategies. Further functionalization of the acid cores with amines using polymer-supported coupling reagents or with alcohols utilizing Mitsunobu chemistry provides the desired amides or esters, respectively.     

The aldol reaction of silyl enol ethers within a micro reactor

We have demonstrated the use of silyl enol ethers in the aldol reaction within a micro reactor. Quantitative conversion of the silyl enol ether to a beta-hydroxyketone was observed in a 20 min period compared to traditional batch systems, where quantitative yields were only obtained when extended reaction times of 24 h were employed.     

闪蒸分离的低温液相甲醇合成的研究

为了强化传质和反应操作,同时实现反应产物与浆液的分离,使用CuCr/CH3ONa催化体系,在鼓泡浆液反应器(BCSR)、闪蒸塔(FC)和浆液循环泵组成的反应系统（BCSR FC）中考察了低温甲醇合成的反应性能。初始浆液由铜铬催化剂、甲醇钠溶液、乳化剂OP 10和液相介质二甲苯组成。在BCSR:4.2MPa～4.6MPa,110℃～120℃(反应段)100℃～110℃(扩大段),入口气速0.35cm/s～0.40cm/s;FC:0.25MPa～0.40MPa,80℃～90℃,浆液循环量50L/h下, 100h实验期间,合成气转化率、CO转化率和H2转化率分别从最高的71.0％、79.1％和67.5％降到17.8％、35.0%和12.1%。催化体系失活的主要原因是CH3ONa 和MeF反应生成甲酸钠。液体产物由DME 1.23%、甲醇79.52%、MeF 19.25%组成。甲醇＋MeF的选择性大于98％。以系统中催化剂为基准,液体产物的产率则为0.166g/gcat·h; BCSR中CuCr催化剂的液体产物的产率为0.336g/gcat·h。     

Stereoselective alkylation of an Evans auxiliary derivative within a pressure-driven micro reactor

A simple technique for the diastereoselective alkylation of a metal stabilised enolate is demonstrated within a pressure-driven micro reactor whereby enhanced diastereoselectivities were obtained compared to batch.     

Microstructure characterization of IG110 and reactor pebble graphite using synchrotron micro X‐ray diffraction 2D maps

Knowledge about the microstructure of nuclear graphite is critical to the understanding of its irradiation behavior in the reactor. Using micro X‐ray diffraction (μXRD) two‐dimensional (2D) maps, the crystallite character of IG110 and reactor pebble graphite was characterized at the submillimeter range with a spatial resolution of about 5 μm. Various structures in the nuclear graphite were identified by comparing the X‐ray diffraction peak intensity, position, and full width at half maximum (FWHM) 2D maps. The two‐peak feature of the FWHM histograms seen in pebble graphite may be related to the raw coke and natural graphite used as raw materials. With these results, it can be concluded that the μXRD 2D map is an effective method to characterize the microstructure of nuclear graphite.     

Methyl esters: an alternative protecting group for the synthesis of O-glycosyl amino acid building blocks

The glycosyl amino acids α-GalNAc-Ser and α-GalNAc-Thr are fundamental building blocks for glycopeptide synthesis, Schmidt’s synthesis method often being chosen for this purpose. Methyl esters used as orthogonal carboxylic acid protecting group in this procedure were found to be an efficient and inexpensive alternative to other groups. The mild selective methyl ester deprotection by LiI improved the efficiency of the synthesis method.     

脱氢丙氨酸酯、酰胺的合成方法研究

本文从Boc保护的丝氨酸出发，经两种途径合成了脱氢丙氨酸酯及其酰胺衍生物，两种合成方法操作简便、产率高、反应条件温和。     

Preparative synthesis of veratraldehydeoxime esters

Preparative syntheses of veratraldehydeoxime esters 6–24, available fragrances produced from vanillin (1), in 82–92% yield from veratraldehydeoxime (3) were developed. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 558–560, November–December, 2008.     

Polymer-bound diazonium salts for the synthesis of diazoacetic esters

Starting from Merrifield resin, various polymer-bound diazonium salts were prepared. Upon treatment with amino acid esters, resulting the appropriate triazenes, the corresponding diazoacetic esters were formed by basic cleavage. Scope and limitation of this transformation were investigated.