New synthetic strategy for facile synthesis of functional polymers by one‐pot combination of controlled radical polymerization and enzymatic reaction

One‐pot synthesis in organic chemistry is deeply rooted in people's minds due to its huge improvement in efficiency compared with conventional stepwise synthesis. Nowadays, such a concept has also been shifted to polymer chemistry by one‐pot introducing compatible or orthogonal organic reactions with polymerizations for facilely synthesizing or modifying polymers. This review systematically summarizes recent developments in the one‐pot combination of enzymatic reactions with controlled radical polymerization to prepare functional polymers. © 2015 Society of Chemical Industry     

One‐pot synthesis of polyetherimides from bis(chlorophthalimide) and dichlorodiphenylsulfone in diphenylsulfone

Polyetherimides and copolymers have been synthesized in one pot from bis(chlorophthalimide), dichlorodiphenylsulfone, and bisphenolate using diphenylsulfone as the solvent. The inherent viscosities of the obtained polyimides are in the range of 0.32–0.72 dL/g, and the structures of polyimides were confirmed by IR and elemental analyses. All of the polyimides have good solubility in common organic solvents. The 5% weight‐loss temperatures of the polyimides were 429–507°C in air. The glass transition temperatures (T_g) of 4,4′‐(9‐fluorenylidene) diphenol‐based polyimides are in the range of 253–268°C. The T_g of bisphenol A‐based polyimides is in the range of 198–204°C, while the T_g change inconspicuously when the ratios of diphenylsulfone increase. The wide‐angle X‐ray diffraction showed that all polyimides prepared are amorphous. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4584–4588, 2006     

Convenient Preparation of Chiral α,β‐Epoxy Ketones via Claisen–Schmidt Condensation‐Epoxidation Sequence

A novel Clasisen–Schmidt condensation‐epoxidation sequence of aldehydes and ketones was developed to produce a series of chiral α,β‐epoxy ketones under asymmetric phase‐transfer catalytic conditions. The organocatalytic method reported here can afford chiral α,β‐epoxy ketones under mild conditions with moderate to good yields and up to 96 % ee.     

Silver‐Catalyzed One‐Pot Cyclization Reaction of Electron‐ Deficient Alkynes and 2‐Yn‐1‐ols: An Efficient Domino Process to Polysubstituted Furans

Transition metal‐catalyzed domino reactions have been used as powerful tools for the preparation of polysubstituted furans in a one‐pot manner. In this paper, an efficient synthetic method was developed for the construction of tri‐ or tetrasubstituted furans from electron‐deficient alkynes and 2‐yn‐1‐ols by a silver‐catalyzed domino reaction. It is especially noteworthy that a 2,3,5‐trisubstituted 4‐ynyl‐furan was formally obtained in an extremely direct manner without tedious stepwise synthesis. In addition, regio‐isomeric furans were observed when substituted aryl alkynyl ketones were employed. This methodology represents a highly efficient synthetic route to electron‐deficient furans for which catalytic approaches are scarce. The reaction proceeds efficiently under mild conditions with commercially available catalysts and materials.     

Amine‐Catalyzed Asymmetric Epoxidation of α,β‐Unsaturated Aldehydes

The direct organocatalytic enantioselective epoxidation of α,β‐unsaturated aldehydes with different peroxides is presented. Proline, chiral pyrrolidine derivatives, and amino acid‐derived imidazolidinones catalyze the asymmetric epoxidation of α,β‐unsaturated aldehydes. In particular, protected commercially available α,α‐diphenyl‐ and α,α‐di(β‐naphthyl)‐2‐prolinols catalyze the asymmetric epoxidation reactions of α,β‐unsaturated aldehydes with high diastereo‐ and enantioselectivities to furnish the corresponding 2‐epoxy aldehydes in high yield with up to 97:3 dr and 98 % ee. The use of non‐toxic catalysts, water and hydrogen peroxide, urea hydroperoxide or sodium percarbonate as the oxygen sources could make this reaction environmentally benign. In addition, one‐pot direct organocatalytic asymmetric tandem epoxidation‐Wittig reactions are described. The reactions were highly diastereo‐ and enantioselective and provide a rapid access to 2,4‐diepoxy aldehydes. Moreover, a highly stereoselective one‐pot organocatalytic asymmetric cascade epoxidation‐Mannich reaction, which proceeds via the combination of iminium and enamine activation, is presented. The mechanism and stereochemistry of the amino acid‐ and chiral pyrrolidine‐catalyzed direct asymmetric epoxidation of α,β‐unsaturated aldehydes are also discussed.     

Novel lipase isolated from a Pseudomonas strain and its application in the synthesis of S(+)‐2‐O‐benzylglycerol‐1‐acetate

Isolation of a novel microbial lipase (EC 3.1.1.3) having specific catalytic activity for the synthesis of optically pure 2‐O‐benzylglycerol‐1‐acetate, the building block for the preparation of many β‐blockers, phospholipase A2 inhibitors and other biologically active compounds was the aim of this investigation. A Pseudomonas (strain G6), recently isolated from soil, produced an extracellular lipase. SDS–PAGE analysis showed that the lipase protein was a hexamer. The molecular weight of the sub‐units of the lipase protein were 10, 19, 29, 30, 47 and 53. The catalytic activity of the lipase was exploited for the synthesis of 2‐O‐benzylglycerol‐1‐acetate from 2‐O‐benzylglycerol through transesterification using vinyl acetate as acylating agent. High selectivity of the lipase towards the monoacetate product was demonstrated. A 97% enantiomeric excess (ee) of S(+)‐2‐O‐benzylglycerol‐1‐acetate was obtained when the reaction was carried out at room temperature with shaking. The lipase was highly active in anhydrous organic microenvironments and in non‐polar organic solvents with log P values above 2.5. © 2002 Society of Chemical Industry     

Yeast‐mediated enantioselective synthesis of chiral R‐(+)‐ and S‐(−)‐1‐phenyl‐1‐butanol from prochiral phenyl n‐propyl ketone in hexane–water biphasic culture

BACKGROUND: The hydrophobic phenyl n‐propyl ketone was used as a model compound to examine alcohol dehydrogenase activity in Saccharomyces cerevisiae mediated cell culture. Parameters such as pH, hexane‐to‐water volume percentage, and the amount of cofactor Zn²⁺ ion for either cell growth or reduction were studied to see their effect on the enantioselectivity toward the product R‐(+)‐ or S‐(?)‐1‐phenyl‐1‐butanol. RESULTS: The pH for cell growth in aqueous culture was 7.0, while the pH for reduction in the aqueous portion of the biphasic culture was 5.0. Without Zn²⁺ ion the biphasic cultures of middle to high hexane‐to‐water volume percentage exhibited an R‐(+)‐1‐phenyl‐1‐butanol enantiomeric excess of 53.7% to > 99%. Without Zn²⁺ ion the biphasic cultures at low hexane‐to‐water volume percentage possessed an S‐(?)‐1‐phenyl‐1‐butanol enantiomeric excess of 14.5–46.5%. Exclusively, the enantioselectivity for biphasic cultures containing Zn²⁺ ion was an S‐(?)‐1‐phenyl‐1‐butanol enantiomeric excess of 27.5% to > 99%. Reduction mediated in aqueous culture with varied amount of Zn²⁺ ion by the yeast Candida utilis also showed an S‐(?)‐1‐phenyl‐1‐butanol enantiomeric excess of 79.2–95.4%. CONCLUSION: The enantioselectivity of S. cerevisiae mediated biphasic culture reduction of phenyl n‐propyl ketone can be manipulated through the cofactor Zn²⁺ ion and the hexane volume percentage of the biphasic culture. Copyright © 2008 Society of Chemical Industry     

Lipase‐catalyzed dynamic hydrolytic resolution of (R,S)‐2,2,2‐trifluoroethyl α‐chlorophenyl acetate in water‐saturated isooctane

The hydrolytic resolution of (R,S)‐2,2,2‐trifluoroethyl α‐chlorophenylacetate in water‐saturated isooctane containing Lipase MY(I) at 35 °C is selected as the best reaction condition for producing (R)‐α‐chlorophenyl acetic acid. The kinetic constants, and hence an enantiomeric ratio of 33.6, are estimated and employed for the modeling of time‐course conversions of both substrates by considering product inhibition and enzyme deactivation effects. A successful dynamic kinetic resolution is also achieved, giving the desired (R)‐α‐chlorophenylacetic acid of 93.0% yield and ee_P = 89.5% when 80 mmol dm^?3 trioctylamine acting as the racemization catalyst and enzyme activator is initially added. Copyright © 2006 Society of Chemical Industry     

A New One‐Pot Synthesis of Polysubstituted Indoles from Pyrroles and β‐Nitroacrylates

The reaction of β‐nitroacrylates with pyrroles, under solvent‐ and catalyst‐free conditions, allows the formation of Friedel–Crafts adducts which, after in situ treatment with Amberlyst 15 in isopropyl alcohol under reflux, provide polysubstituted indoles, via a benzannulation reaction, in a one‐pot process.     

One‐pot synthesis of photosensitive dendrimer‐like polystyrenes from simultaneous copper(I)‐catalyzed azide–alkyne cycloaddition and atom transfer radical polymerization

Dendrimer‐like polystyrenes (PSs) containing azobenzene moieties/core were prepared by one‐pot copper(I)‐catalyzed azide–alkyne cycloaddition (CuAAC) and atom transfer radical polymerization (ATRP) in the presence of PS with terminal azide groups, styrene monomers, 2,4‐dibromoisobutyrate‐4′‐propynyloxyazobenzene, copper(I) bromide and ligand. The successful preparation of the dendrimer‐like PSs was confirmed using gel permeation chromatography and ¹H NMR and Fourier transform infrared spectroscopy. The dendrimer‐like PSs prepared from one‐pot CuAAC and ATRP exhibit a well‐defined and controlled molecular structure in both whole macromolecules and the branches, which is attributed to the controlled character of ATRP and the quantitative yield of click chemistry. The dendrimer‐like PSs prepared also exhibit good photo‐isomerization properties due to the incorporation of azobenzene units within the dendrimers. Copyright © 2012 Society of Chemical Industry     

Copper(I)‐Catalyzed One‐Pot Synthesis of 2‐Iminobenzo‐ 1,3‐oxathioles from ortho‐Iodophenols and Isothiocyanates

A novel and efficient formation of 2‐iminobenzo‐1,3‐oxathioles from readily available precursors via a copper(I)‐catalyzed one‐pot cascade process has been developed. Various 2‐iminobenzo‐1,3‐oxathioles, which might be useful in pharmaceutical and biochemical areas, were conveniently synthesized in good to excellent yields.     

Kinetics and modeling of fructo‐oligosaccharide synthesis by immobilized fructosyltransferase from Rhodotorula sp.

BACKGROUND: Fructosyltransferase synthesizes fructo‐oligosaccharides from sucrose. Data used in this work were obtained by an enzyme produced by Rhodotorula sp., a microorganism isolated from fruit samples from the Brazilian Atlantic Forest, which was immobilized in an inorganic support, consisting of a niobium and graphite alloy. RESULT: All essays were conducted using enzymes at two purification grades, highly and partially purified enzymes, as comparison. The results were not significantly different between the two enzyme grades, mainly concerning the final fructo‐oligossacharides yield, which were around 46%. Concerning the kinetics, the enzyme follows the Michaelis–Menten equation with inhibition by sucrose (above 60%). Also, a competitive inhibition by glucose was observed on sucrose, kestose and nystose uptakes. The immobilization of the enzyme was by ion exchange on the surface of the particles, since the support is a charged and compact solid, with negligible porosity. The mathematic model includes mass balances, considering the resistance to external mass transfer. A parameter sensitivity analysis and parameter fitting were performed by simulations and the model was validated by comparison with experimental data. CONCLUSION: The model fitted experimental data well, with deviations lower than 5% concerning FOS concentrations, indicating that it can be used in the design and control of bioreactors, either using purified or partially purified enzyme. Copyright © 2010 Society of Chemical Industry     

Kinetic study of ethyl octyl ether formation from ethanol and 1‐octanol on Amberlyst 70

An option to introduce bioethanol to diesel, improving at the same time its fuel quality, is by adding ethyl octyl ether (EOE). It can be obtained successfully by the dehydration reaction between ethanol and 1‐octanol over acidic ion‐exchange resins. In the present work, the kinetic study of EOE synthesis on Amberlyst 70 in the liquid phase is performed in a 20‐cm³ fixed‐bed reactor and in a 100‐cm³ batch reactor at 423–463 K and 2.5 MPa. EOE synthesis takes place together with diethyl ether (DEE) formation as main side reaction. A mechanistic kinetic model in terms of component activities is proposed for EOE synthesis (E_a=105 ± 4 kJ/mol) and for DEE formation (E_a =100 ± 5 kJ/mol). Reaction rates were highly inhibited by the adsorption of the formed water on Amberlyst 70. The inhibitor effect of water is well represented as a competitive adsorption with alcohols reactants on the catalysts surface. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2918–2928, 2014     

Immobilisation of different Candida rugosa lipases by adsorption onto polypropylene powder: application to chiral synthesis of ibuprofen and trans‐2‐phenyl‐1‐cyclohexanol esters

Candida rugosa lipases (CRLs) were immobilised by adsorption onto a commercial polypropylene powder EP100?. Two commercial CRLs from Sigma and Amano were used together with two CRLs obtained by fed‐batch fermentation using oleic acid as a carbon source (UAB‐CRL). Significant differences were observed in the isotherm adsorption patterns for the commercial and fermented lipases, probably caused by differences in their polysaccharide content. The commercial lipases showed a classical Langmuir adsorption pattern, whereas fed‐batch produced lipases with high polysaccharide content tended to conform to a BET multilayer adsorption equation. Immobilised CRLs also showed different behaviour in the resolution of two interesting pharmaceutical products: ibuprofen and trans‐2‐phenyl‐1‐cyclohexanol (TPCH) in the enantioselective esterification reaction in organic media. In the case of ibuprofen, CRLs showed important differences in terms of esterification rate, probably due to diffusional limitation effects caused by the high polysaccharide content present in UAB‐CRLs. In the case of TPCH, however, polysaccharide content did not appear to influence the esterification rate. A high enantioselective esterification was observed for all CRLs tested in the resolution of both products. © 2002 Society of Chemical Industry     

Hydrogenation of α‐Keto Ethers: Dynamic Kinetic Resolution with a Heterogeneous Modified Catalyst and a Heterogeneous Base

The first successful example of the asymmetric hydrogenation of substituted α‐keto ethers with Cinchona‐modified Pt/Al₂O₃ is reported. In the absence of an additional base, kinetic resolution of the racemic starting material was observed with high diastereoselectivity and ee's up to 98% at conversions of <50%. Addition of KOH gave a strong reaction acceleration but racemic product. Immobilization of OH ^– on solid ion exchangers resulted in the desired dynamic kinetic resolution, and ee's of >80% were obtained at >95% conversion. These effects are rationalized on the basis of a simple kinetic and structural model.