Synthetic Modifiers for Platinum in the Enantioselective Hydrogenation of Ketopantolactone: A Test for the Mechanistic Models of Ketone Hydrogenation

Various derivatives of (R)‐1‐(1‐naphthyl)ethylamine have been synthesized and tested as chiral modifiers of Pt/alumina in the enantioselective hydrogenation of ketopantolactone. The best modifiers (ee up to 79%) possess an ester function in the α‐position to the amino group. The modifiers performed far better in AcOH than in toluene, indicating that protonation of the N atom is important in enantioselection. The striking non‐linear behaviour of modifier mixtures with cinchonine indicates that the alkaloid adsorbs much stronger on Pt than the naphthylethylamine derivatives. Two mechanistic models are proposed for interpretation of the results, involving an N H O or N⁺ H O bond between the amine‐type modifier and the keto carbonyl O atom of ketopantolactone, in apolar and protic media, respectively. In both cases the H atom originates from the modifier and not from the substrate (“half‐hydrogenated‐state”). The higher ee achieved in acidic medium is attributed to the better proton donor ability of the protonated amine modifiers. The models are applicable also to the hydrogenation of ethyl pyruvate.     

Reactive extraction of propionic acid using tri‐n‐octylamine,tri‐n‐butyl phosphate and aliquat 336 in sunflower oil as diluent

BACKGROUND : Propionic acid is widely used in chemical and allied industries and can be produced by biocultivation in a clean and environmentally friendly route. Recovery of the acid from the dilute stream from the bioreactor is an economic problem. Reactive extraction is a promising method of recovering the acid but suffers from toxicity problems of the solvent employed. There is thus a need for a non‐toxic solvent or a combination of less toxic extractants in a non‐toxic diluent that can recover acid efficiently. RESULTS: The effect of different extractants (tri‐n‐butylphosphate (TBP), tri‐n‐octylamine (TOA) and Aliquat 336) and their mixed binary solutions in sunflower oil diluent was studied to find the best extractant‐sunflower oil combination. Equilibrium complexation constant, K_E, values of 4.02, 3.13 and 1.87 m³ kmol^?1 were obtained for propionic acid extraction using Aliquat 336, TOA and TBP, respectively, in sunflower oil. The effect of different modifiers (1‐decanol, methylisobutyl ketone, butyl acetate and dodecanol) on the extraction was also studied and it was found that modifiers enhance extraction, with 1‐decanol found to be the best. CONCLUSION: The problem of toxicity in reactive extraction can be reduced by using a non‐toxic diluent (sunflower oil) or a modifier in a non‐toxic solvent, with the extractant. The addition of modifiers was found to improve the extraction. Copyright © 2008 Society of Chemical Industry     

Enantioselective hydrogenation of ethyl pyruvate catalysed by cinchonine-modified Pt/Al2O3: tilted adsorption geometry of cinchonine

The enantioselective hydrogenation of ethyl pyruvate (EtPy) was studied on Pt-alumina catalyst modified by cinchonine (CN) and for comparison by cinchonidine (CD) in toluene and in AcOH. The effects of the modifiers concentration on the reaction rate and the enantioselectivity were examined. Using the Engelhard 4759 catalyst under mild experimental conditions (room temperature, hydrogen pressure 1 bar) in the case of CN (S)-ethyl lactate (EtLt) formed in excess (ee) (in AcOH ee_max 88%; in toluene ee_max 72%). In the case of CD (R)-EtLt formed in excess (in AcOH ee_max 93%; in toluene ee_max 84%). The results of H–D exchange measurements and results of modifier mixtures suggest that the compounds responsible for chiral induction are different intermediates, which structure depends mostly on the acidic or non-acidic nature of the hydrogenation medium. The proposed structure of intermediate responsible for enantioselection is an 1:1 CN– or CD–EtPy surface complex in which the quinoline skeleton of CD approximately parallel on the Pt surface while the quinoline plane of CN being tilted relative to the Pt surface under identical experimental conditions.     

Ruthenium(II)‐Catalyzed Regioselective Synthesis of Allyl Ketones from Alkynes and their Silver(I)‐Catalyzed Hydroarylation into γ‐Functionalized Ketones

The regioselective synthesis of β,γ‐unsaturated ketones from terminal alkynes is achieved by cooperative action of tris(acetonitrile)pentamethylcyclopentadieneruthenium hexafluorophosphate [Cp*Ru(NCMe)₃⁺ PF₆⁻] and para‐toluenesulfonic acid catalysts. These allyl ketones undergo direct regioselective hydroarylation/Friedel–Crafts reaction to introduce an electron‐rich aryl group at the γ‐position in the presence of ligand‐free silver triflate (AgOTf) catalyst. Both catalytic reactions take place with atom economy and provide an alternative to the synthesis of a variety of allyl ketones and γ‐arylated ketones.     

Preparation of electrorheological active ionomers from poly(2‐hydroxyethyl methacrylate)‐co‐poly(4‐vinyl pyridine)

In this study, synthesis, characterization, partial hydrolysis, and salt formation of poly(2‐hydroxyethyl methacrylate)‐co‐poly(4‐vinyl pyridine), (poly(HEMA)‐co‐poly‐(4‐VP)) copolymers were investigated. The copolymers were synthesized by free radical polymerization using K₂S₂O₈ as an initiator. By varying the monomer/initiator ratio, chain lengths of the copolymers were changed. The copolymers were characterized by gel permeation chromatography (GPC), viscosity measurements, ¹H and ¹³C NMR and FTIR spectroscopies, elemental analysis, and end group analysis methods. The copolymers were partially hydrolyzed by p‐toluene sulfonic acid monohydrate (PTSA·H₂O) and washed with LiOH_(aq) solution to prepare electrorheological (ER) active ionomers, poly(Li‐HEMA)‐co‐poly(4‐VP). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3540–3548, 2006     

Local structure of network modifier to network former ions in soda‐lime alumino‐borosilicate glasses

The structure of soda‐lime alumino‐borosilicate glass was studied using molecular dynamics simulations of samples of varying compositions containing ~20 000 atoms each. Pair distribution functions (PDFs) of cations to oxygen were used for comparison to available experimental data to evaluate consistency between simulations and experiment. Additional PDFs and coordination of the network forming cations (Al/B/Si) to network modifiers (Ca/Na) were examined, which is difficult to measure experimentally. The results are consistent with available experimental data regarding cation‐oxygen bond lengths and network former to oxygen coordination numbers. Si and Al are predominantly 4‐coordinated, with a small concentration of overcoordinated species similar to experimental data. B varied as 3‐coordinated, BO₃, and 4‐coordinated, BO₄, as a function of the amount of Ca²⁺ and Na⁺ present, the ratio of Al₂O₃ to B₂O₃, and the fictive temperature of the sample, similar to experimental data. The simulations provide new information regarding the locations on the network modifiers to the +3 cations, Al and B. For instance, one Al ion can have multiple Na within 4 Å, but also the Na can be within 4 Å of several +3 cations. Such results would indicate a greater complexity of local structure that goes beyond the stoichiometric one +1 modifier ion near one +3 network former or one +2 modifier near two +3 formers in tetrahedral sites.     

Synthesis of Diastereomeric 1,4‐Diphosphine Ligands Bearing Imidazolidin‐2‐one Backbone and Their Application in Rh(I)‐Catalyzed Asymmetric Hydrogenation of Functionalized Olefins

The diastereomeric 1,4‐diphosphine ligands, (S,S,S,S)‐ 1a , (R,S,S,R)‐ 1b and (R,S,S,S)‐ 1c , with the imidazolidin‐2‐one backbone were synthesized, and utilized for an investigation of the effects of backbone chirality on the enantioselectivity in the Rh(I)‐catalyzed hydrogenation of various functionalized olefinic substrates. It was found that the catalytic efficiencies are largely dependent on the configurations of the α‐carbons to phosphine. Thus, the Rh complex of the pseudo‐C₂‐symmetrical diphosphine, (R,S,S,S)‐ 1c , showed excellent enantioselectivities (93.0–98.6% ees) in the hydrogenations of a broad spectrum of substrates, and especially in the hydrogenations of methyl α‐(N‐acetyamino)‐β‐arylacrylates (95.3–97.0% ees). However, the enantioselectivities obtained with the C₂‐symmetrical (R,S,S,R)‐ 1b were largely dependent on the substrate (19.8–97.3% ees). The Rh complex of ligand 1a having the (S,S,S,S)‐configuration showed the lowest catalytic efficiency for all of the substrates examined (0–84.8% ees).     

Non‐Isothermal Kinetic Study of the Thermal Decomposition of Melamine 3‐Nitro‐1,2,4‐triazol‐5‐one Salt

Study on thermal behavior of 3‐nitro‐1,2,4‐triazol‐5‐one (NTO) salts was required to obtain important data for application purposes. These compounds have been shown to be useful intermediates for gun propellant ingredients, high energetic ballistic modifiers for solid propellants and other potential applications. In this paper, thermal decomposition and non‐isothermal kinetics of melamine 3‐nitro‐1,2,4‐triazol‐5‐one salt (MNTO) were studied under non‐isothermal conditions by DSC and TG methods. The kinetic parameters were obtained from analysis of the DSC and TG curves by Kissinger and Ozawa methods. The critical temperature of thermal explosion (T_b) was 574 K. The results show that MNTO is thermally more stable than NTO when compared in terms of the critical temperature of thermal explosion. Finally, the values of ΔS^#, ΔH^#, and ΔG^# of its decomposition reaction were calculated.     

Synthesis and properties of polystyrene‐b‐poly(ethylene oxide)‐b‐polystyrene triblock copolymers

A series of well‐defined and property‐controlled polystyrene (PS)‐b‐poly(ethylene oxide) (PEO)‐b‐polystyrene (PS) triblock copolymers were synthesized by atom‐transfer radical polymerization, using 2‐bromo‐propionate‐end‐group PEO 2000 as macroinitiatators. The structure of triblock copolymers was confirmed by ¹H‐NMR and GPC. The relationship between some properties and molecular weight of copolymers was studied. It was found that glass‐transition temperature (T_g) of copolymers gradually rose and crystallinity of copolymers regularly dropped when molecular weight of copolymers increased. The copolymers showed to be amphiphilic. Stable emulsions could form in water layer of copolymer–toluene–water system and the emulsifying abilities of copolymers slightly decreased when molecular weight of copolymers increased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 727–730, 2006     

Synthesis and characterization of poly(o‐toluidine) doped with organic sulfonic acid by solid‐state polymerization

Poly (o‐toluidine) (POT) salts doped with organic sulfonic acids (β‐naphthalene sulfonic acid, camphor sulfonic acid, and p‐toluene sulfonic acid) were directly synthesized by using a new solid‐state polymerization method. The FTIR spectra, ultraviolet visibility (UV–vis) absorption spectra, and X‐ray diffraction patterns were used to characterize the molecular structures of the POT salts. Voltammetric study was done to investigate the electrochemical behaviors of all these POT salts. The FTIR and UV–vis absorption spectra revealed that the POT salts were composed of mixed oxidation state phases. All POT salts contained the conducting emeraldine salt (half‐oxidized and protonated form) phase; the pernigraniline (fully oxidized form) phase is predominant in POT doped with β‐naphthalene sulfonic acid, and POT doped with p‐toluene sulfonic acid had the highest doping level. The X‐ray diffraction patterns showed that the obtained POT doped with organic sulfonic acids were lower at crystallinity. The conductivity of the POT salts were found to be of the order 10^?3‐10^?4 S/cm. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1630–1634, 2005     

Facile synthesis of 5,8‐linked quinoline‐based copolymers

Coupling quinoline at its 5,8‐positions provides a facile way to copolymerize quinoline with other conjugated moieties without breaking conjugation. Model compounds containing quinoline units, either at the periphery or in the core, were synthesized and one of them was characterized by X‐ray diffraction. Copolymers of quinoline and 9,9‐dialkylfluorene (R = n‐octyl or 2‐ethylhexyl) were synthesized in good yield by palladium‐catalysed Suzuki cross‐coupling. The copolymers are highly soluble in common organic solvents and gel permeation chromatography measurements against polystyrene standards showed the number‐average molecular weight to be in the range (1.02–2.06) × 10⁴ g mol^?1. Both copolymers emit in the blue region with an emission maximum centred at 435 nm. Copyright © 2012 Society of Chemical Industry     

Energy‐transfer method to study vapor‐induced latex film formation

Nonradiative energy transfer method was used to study latex film formation induced by organic solvent vapor. Seven different films with the same latex content were prepared separately from poly(methyl methacrylate) (PMMA) particles and exposed to ethyl benzene, toluene, chloroform, dichloromethane, tetrahydrofuran, and acetone vapor in seven different experiments. Energy‐transfer experiments were carried out between PMMA‐bound naphthalene (N) and pyrene (P) during vapor‐induced film formation. Latex films were prepared from equal amounts of N‐ and P‐labeled latex particles, and steady state spectra of N and P were monitored during film formation. It was observed that the P to N intensity ratio, I_P/I_N, increased as the vapor exposure time increased. The Prager–Tirrell (PT) model was employed to obtain back‐and‐forth frequencies, ν, of the reptating PMMA chains during latex film formation induced by solvent vapor. ν values were obtained and found to be correlated with the solubility parameter, δ. Polymer interdiffusion obeyed the t^1/2 law during film formation. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 632–645, 2002; DOI 10.1002/app.10346     

Liquid/solid two‐phase carbonization of low‐molecular‐weight chloro‐/bromo‐hydrocarbons

A novel liquid/solid two‐phase reaction has been discovered that enables destruction of a series of low‐molecular‐weight chloro‐/bromo‐hydrocarbons to carbon‐based materials. The solid phase is anhydrous potassium hydroxide and the liquid phase is a benzene or tetrahydrofuran solution of halide and contains a certain amount of tetrabutyl ammonium bromide (TBAB) as phase transfer catalyst. The structure of the carbon‐based materials have been characterized by elemental analysis, Fourier transform infrared (FT‐IR), FT‐Raman, and X‐ray photoelectron spectroscopies, and their morphologies have been examined by wide‐angle X‐ray diffraction and transmission electron microscopy. The results indicate that the products are amorphous nanoparticles and contain mainly elemental carbon. They consist of sp, sp², and sp³ carbon atoms simultaneously and can be regarded as carbyne analogues. This work provides a convenient method for synthesizing new carbon‐based materials in relatively high yields. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1510–1515, 2000     

Morphology and mechanical properties of ABS blends prepared from emulsion‐polymerized PB‐g‐SAN impact modifier with AIBN as initiator

A series of PB‐g‐SAN impact modifiers (polybutadiene particles grafted by styrene and acrylonitrile) are synthesized by seed emulsion copolymerization initiated by oil‐soluble initiator, azobisiobutyronitrile (AIBN). The ABS blends are obtained by mixing SAN resin with PB‐g‐SAN impact modifiers. The mechanical behavior and the phase morphology of ABS blends are investigated. The graft degree (GD) and grafting efficiency (GE) are investigated, and the high GD shows that AIBN has a fine initiating ability in emulsion grafting of PB‐g‐SAN impact modifiers. The morphology of the rubber particles is observed by the transmission electron microscopy (TEM). The TEM photograph shows that the PB‐g‐SAN impact modifier initiated by AIBN is more likely to form subinclusion inside the rubber particles. The dynamic mechanical analysis on ABS blends shows that the subinclusion inside the rubber phase strongly influences the T_g, maximum tan δ, and the storage modulus of the rubber phase. The mechanical test indicates that the ABS blends, which have the small and uniform subinclusions dispersed in the rubber particles, have the maximum impact strength. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Iron‐Catalysed sp3–sp3 Cross‐Coupling Reactions of Unactivated Alkyl Halides with Alkyl Grignard Reagents

Iron‐catalysed sp³–sp³ Kumada coupling with primary and secondary alkyl halides (RX) and alkyl Grignard reagents has been achieved in low to good yields depending on the nature of the R group.     

A Thermostable Aldolase for the Synthesis of 3‐Deoxy‐2‐ulosonic Acids

A stereochemically promiscuous 2‐keto‐3‐deoxygluconate aldolase has been used as an efficient biocatalyst to catalyse the aldol reaction of pyruvate with C₃‐ and C₄‐aldoses to afford syn‐ and anti‐3‐deoxy‐2‐ulosonic acids in poor to good de. A continuous flow bioreactor containing immobilised aldolase has been developed that enables gram quantities of C₆‐ and C₇‐3‐deoxyhept‐2‐ulosonic acids to be produced in an efficient manner.     

Organocatalytic Asymmetric Aldol Reaction of Ketones with β,γ‐Unsaturated α‐Keto Esters: An Efficient Access to Chiral Tertiary Alcohol Skeletons

This update describes a highly efficient organocatalytic aldol reaction of ketones and β,γ‐unsaturated α‐keto esters for constructing the chiral tertiary alcohol motif. With the application of 9‐amino(9‐deoxy)epi‐Cinchona alkaloid and an acidic additive as catalysts, both acyclic and cyclic ketones react with β,γ‐unsaturated α‐keto esters smoothly to afford aldol adducts in good to excellent yields and asymmetric induction. This protocol offers a new pathway for the construction of adjacent chiral carbon centers and the synthesis of chiral β‐hydroxy carbonyl compounds.     

Toughening of cyanate ester resin by N‐phenylmaleimide–N‐(p‐hydroxy)phenyl‐maleimide–styrene terpolymers and their hybrid modifiers

N‐Phenylmaleimide–N‐(p‐hydroxy)phenylmaleimide–styrene terpolymer (HPMS), carrying reactive p‐hydroxyphenyl groups, was prepared and used to improve the toughness of cyanate ester resins. Hybrid modifiers composed of N‐phenylmaleimide–styrene copolymer (PMS) and HPMS were also examined for further improvement in toughness. Balanced properties of the modified resins were obtained by using the hybrid modifiers. The morphology of the modified resins depends on HPMS structure, molecular weight and content, and hybrid modifier compositions. The most effective modification of the cyanate ester resin was attained because of the co‐continuous phase structure of the modified resin. Inclusion of the modifier composed of 10 wt% PMS (M_w 136 000 g mol^?1) and 2.5 wt% HPMS (hydroxyphenyl unit 3 mol%, M_w 15 500 g mol^?1) led to 135% increase in the fracture toughness (K_IC) for the modified resin with a slight loss of flexural strength and retention of flexural modulus and glass transition temperature, compared with the values for the unmodified resin. Furthermore, the effect of the curing conditions on the mechanical and thermal properties of the modified resins was examined. The toughening mechanism is discussed in terms of the morphological and dynamic viscoelastic behaviour of the modified cyanate ester resin system. © 2001 Society of Chemical Industry     

N,N′‐Dioxide‐Magnesium Ditriflate Complex‐Catalyzed Asymmetric α‐Hydroxylation of β‐Keto Esters and β‐Keto Amides

The highly catalytic asymmetric α‐hydroxylation of 1‐tetralone‐derived β‐keto esters and β‐keto amides using tert‐butyl hydroperoxide (TBHP) as the oxidant was realized by a chiral N,N′‐dioxide‐magnesium ditriflate [Mg(OTf)₂] complex. A series of corresponding chiral α‐hydroxy dicarbonyl compounds was obtained in excellent yields (up to 99%) with excellent enantioselectivities (up to 98% ee). The products were easily transformed into useful building blocks and the precursor of daunomycin was achieved in an asymmetric catalytic way for the first time.     

Gold Catalysis: β‐Ketonaphthalenes via Molecular Gymnastics of 1,6‐Diyne‐4‐en‐3‐ols

1,6‐Diyne‐4‐en‐3‐ols with one terminal alkyne were applied as test substrates for a possible dual catalyzed cyclization. Instead of a dual catalysis cycle, naphthyl ketone derivatives were obtained as single products. The regioselectivity of the obtained products is unprecedented. Instead of the expected naphthyl ketones bearing the keto group in the α‐position, the keto group is positioned in the ß‐position of the naphthyl skeleton by a complex rearrangement of the starting materials.