Radical deoxygenation of alcohols and intermolecular carbon-carbon bond formation with surfactant-type radical chain carriers in water

An efficient and mild method is developed for radical deoxygenation of alcohols and formation of carbon-carbon bonds in water without adding additives such as surfactants. The reaction was applied to synthesis of 2′,3′-didehydro-2′,3′-dideoxynucleosides that are potent anti-HIV agents. The reaction afforded environmentally benign reaction conditions.     

Acryloylated α,/β-poly (N-hydroxyethyl)-DL-aspartamide and α,β-polyasparthydrazide. Synthesis, characterization and radiation formation of polymeric networks

 In the present study the derivatization of two water-soluble and synthetic polymers, such as α,β-poly(N-hydroxyethyl)-DL-aspartamide (PHEA) and α,β-polyasparthydrazide (PAHy), with glycidylmethacrylate (GMA) is described. This reaction allowed the introduction of double bonds in the macromolecular chains of PHEA and PAHy in order to make easier the crosslinking by a radical mechanism. Different parameters affected the reaction of derivatization, such as reaction pH, GMA concentration and reaction time. As far as PHEA is concerned the amount of GMA linked to the polymer increased until reaching a plateau. On the contrary, the reaction of PAHy with GMA proceeded with a zero order kinetics and the GMA amount in the polymer increased regularly. Some aqueous solutions of PHEA-GMA and PAHy-GMA copolymers at various GMA content were submitted to gamma radiation processing, thus obtaining crosslinked structures. The derivatization of PHEA and PAHy with GMA was a convenient method to introduce insaturations in their chains and it allowed to obtain gels at lower doses with respect to the starting polymers. Received: 2 April 1996 Accepted: 30 June 1996     

Fluorometric Determination of Fructose, Glucose, and Sucrose Using Zirconyl Chloride

Zirconyl chloride upon hydrolysis in water to form Zr(OH)⁺ has been found to react to form a fluorescent derivative with not only a ketose such as fructose but also a hexose such as glucose and the disaccharide sucrose. When reaction conditions such as a temperature of 99°C and a time of 60 min are used, detection limits below 1 μg/mL are possible. All three zirconyl–sugar derivatives show very similar absorbance and fluorescence spectra, indicating a common mechanism involving formation of an enediol which can be complexed with ZrOH⁺ is likely. Because the reactivity order is glucose < sucrose < fructose, the reaction can be made selective for fructose at a lower reaction temperature and time such as 60°C at 5 min. Because interference from ascorbic acid and caffeine is also avoided, the fluorescent determination of fructose in soft drink samples after simply a dilution step is possible. We have also employed this reaction for flow injection analysis (FIA) using a polystyrene–divinylbenzene-packed HPLC column as a mixing device. Using a 0.01 M HClO₄ with 1% zirconyl chloride carrier, we obtained a linear calibration curve from 2 to 30 μg/mL with a correlation coefficient of 0.994. A detection limit less than 2 μg/mL was possible. A comparison of results for the FIA of soft drinks with the enzymatic method involving fructose-5-dehydrogenase confirmed the FIA method was quite specific for fructose.     

Ecofriendly and efficient procedure for hetero-Michael addition reactions with an acidic ionic liquid as catalyst and reaction medium

Abstract  

1-Methylimidazolium trifluoroacetate ([Hmim]TFA) is reported as a cost-effective catalyst for a simple and environmentally benign hetero-Michael reaction. [Hmim]TFA works both as reaction medium and catalyst. The reaction is applicable to various aromatic sulfur and nitrogen nucleophiles. This method has advantages such as high yields, short reaction time, and simple workup. The catalyst could be recycled several times without any loss of activity.     

Conjugate addition of aromatic amines to ethenetricarboxylates

The conjugate addition of amines is considered to be a useful reaction in synthetic organic chemistry. The reaction of reactive electrophilic olefins, ethenetricarboxylates, and aromatic amines with and without catalytic Lewis acids such as ZnCl₂ and ZnBr₂ at room temperature gave amine adducts in high yields. The products were converted to α-amino acid, dl-aspartic acid derivatives. Using Lewis acids such as Sc(OTf)₃ and Zn(OTf)₂ at higher temperature (40-80 °C), the reaction of ethenetricarboxylates and N-methylaniline gave an aromatic substitution product. A catalytic enantioselective conjugate addition using a chiral Lewis acid was also investigated. For example, the reaction of 1,1-diethyl 2-tert-butyl ethenetricarboxylate with N-methylaniline in the presence of chiral bisoxazoline-Cu(II) complex in THF at −20 °C for 17 h gave an amine adduct in 91% yield and 78% ee. On the other hand, the reaction with aniline and primary aniline derivatives gave adducts with almost no ee%.     

Nickel nanoparticle-catalyzed facile and efficient one-pot synthesis of polyhydroquinoline derivatives via Hantzsch condensation under solvent-free conditions

Polyhydroquinoline derivatives have been prepared efficiently in a one-pot synthesis via Hantzsch condensation using nanosized Nickel (Ni) as a heterogeneous catalyst. The present method does not involve any hazardous organic solvents or catalysts. The smaller size of Ni (80 ± 0.5 nm) having a higher surface to volume ratio has promising features for the reaction response such as the shortest reaction time, excellent product yields, simple work-up procedure, and purification of products by non-chromatographic methods.     

Reduction of aromatic compounds with Al powder using noble metal catalysts in water under mild reaction conditions

In water, Al powder becomes a powerful reducing agent, transforming in cyclohexyl either one or both benzene rings of aromatic compounds such as biphenyl, fluorene and 9,10-dihydroanthracene under mild reaction conditions in the presence of noble metal catalysts, such as Pd/C, Rh/C, Pt/C, or Ru/C. The reaction is carried out in a sealed tube, without the use of any organic solvent, at low temperature. Partial aromatic ring reduction was observed when using Pd/C, the reaction conditions being 24 h and 60 °C. The complete reduction process of both aromatic rings required 12 h and 80 °C with Al powder in the presence of Pt/C.     

Nucleophilic trifluoromethylation of aryl halides with methyl trifluoroacetate

When associated with an alkaline halide, such as cesium fluoride or cesium chloride, and Cu(I) species, methyl trifluoroacetate (MTFA) constitutes a valuable trifluoromethylating agent for substituting aromatic (or heteroaromatic) iodides and bromides. The reaction can be carried out in DMF at 180 °C or, better, in sulfolane which allows he reaction to proceed at a lower temperature (from 140 °C).     

Catalytic coprocessing of waste plastics and petroleum residue into liquid fuel oils

Waste plastics of different types were catalytically coprocessed with petroleum residue of light Arabian crude oil in the presence of a number of catalysts. The purpose of the study was to explore effects of various conditions such as catalyst type, amount of catalyst, reaction time, pressure and temperature on the product distribution. The waste plastic studied included low-density polyethylene (LDPE), high-density polyethylene (HDPE), polystyrene (PS) and polypropylene (PP). A series of single (waster plastic with catalyst) and binary (waste plastic and residue with catalyst) reactions were carried out in an autoclave reactor under variable reaction conditions. The reaction conditions used were 1, 3 and 5 wt.% catalysts, 30–120 min reaction time, 400–430 °C reaction temperature and 500–1200 psi hydrogen pressure. The product distribution achieved for residue/plastic/catalyst system showed higher yields of liquid fuels as compared to residue/plastic system. Hydrocarbon gases were formed as well along with heavy oils, insoluble gums and coke. At the reaction conditions of 3 wt.% NiMo catalyst, 90 min reaction time, 1200 psi hydrogen gas pressure, 430 °C temperature and residue to plastic feed ratio of 3:2 (wt.) afforded maximum conversion of the plastics into liquid fuel oils.     

Calorimetric evolution of the early pozzolanic reaction of natural zeolites

The pozzolanic reaction between natural zeolite tuffs, portlandite and water was investigated over the course of the early reaction period up to 3 days. Isothermal conduction calorimetry experiments supplemented by TG/DTG and XRD analyses assisted in the elucidation of the sequence of reaction processes taking place. The calorimetry experiments clearly showed the dependence of the pozzolanic reaction rate and associated heat release on the fineness of the zeolite tuff. Higher external surface areas of pozzolans yield higher total heat releases. Also the exchangeable cation content of the zeolites influences the reaction rate. Release of exchangeable alkalis into solution promotes the pozzolanic reaction by raising the pH and zeolite solubility. The appearance of an exotherm after approximately 3 h of reaction is more conspicuous when alkali-rich zeolites are reacted. This exotherm is conceived to be related to a transformation or rupture of initially formed reaction products covering the zeolite grains. The formation of substantial amounts of ‘stable’ calcium silicate hydrate (C–S–H) and calcium aluminate hydrate (C–A–H) reaction took place after an induction period of more than 6 h. The openness of the zeolite framework affects the proneness of the zeolite to dissolution and thus its reactivity. Open framework zeolites such as chabazite were observed to react much more rapidly than closed framework zeolites such as analcime.     

Tritiation of toluene with HTO

Toluene was tritiated singly or as an equimolar mixture with benzene using HTO in the presence of FeCl₃ as a catalyst. An o, poriented tritium distribution in the ring of toluene at the initial stage of reaction changed into uniform one with elapse of reaction time at 40 °C, whereas such a rapid change was not observed at 5 °C. By tritiation of the equimolar mixture at 6 °C, the partial rate factors were determined as o_f=264, m_f=7, and p_f=189 at the initial stage of the reaction. A possible reaction mechanism is discussed.     

单晶Pb纳米线及纳米粒子的溶液法制备

采用溶液法制备了较高长径比(～100)的铅的均匀纳米线及纳米粒子,并对产物进行了XRD,SEM和TEM表征.探讨了反应温度、反应物浓度及还原剂种类对产物成相及形貌的影响,初步讨论了铅钠米线的形成机制.     

A practical synthesis of 2‐aminobenzothiazoles via copper(I)‐catalyzed tandem reaction of 2‐iodoanilines with isothiocyanates in ionic liquids

A copper(I)‐catalyzed tandem reaction of 2‐iodoanilines with isothiocyanates was achieved in hydrophobic [bmim][PF₆] ionic liquid under mild conditions, generating a variety of 2‐aminobenzothiazoles in good to excellent yields. The tandem reaction that was carried out in [bmim][PF₆] has some obvious advantages such as accelerated reaction rate and increased yield as compared with the reaction run in volatile solvents such as toluene. Furthermore, the CuI/1,10‐phenanthroline catalytic system can be reused up to eight times without loss of activity and efficiency. Copyright © 2016 John Wiley & Sons, Ltd.     

Reduction of nitrobenzene to aniline with carbon monoxide and water

Modified catalytic system composed of selenium and cocatalysts such as pyridine and aniline, applied in the reduction of nitrobenzene to aniline in the presence of carbon monoxide and water is described. The reaction proceeds at 150–200°C and 3–4 MPa gauge pressure. After 1–2 h the reaction is complete, reaching nitrobenzene conversions of up to 98% with selectivity to aniline near 100%.     

l-Proline catalyzed expeditious multicomponent protocol for the synthesis of fused N-substituted-2-pyridone derivatives in aqueous medium

N-substituted-2-pyridone derivatives have many pharmaceutical properties. In our research, we have developed an efficient, green, and multicomponent protocol to synthesize such new fused N-substituted-2-pyridone derivatives. Optimum reaction condition was obtained by employing l-proline as an organocatalyst in aqueous SDS solution at 100 °C. Various 1,3-diketones, including indane 1,3-dione with a range of aromatic and aliphatic amines were utilized to synthesize fused 2-pyridone derivatives. The isolation of a reaction intermediate confirmed our proposed mechanism. Water as a reaction medium improved the scope of the reaction methodology to a large extent.     

One-pot synthesis of β-acetamido-β-arylpropiophenone employing trifluoroacetic acid as an efficient catalyst

Trifluoroacetic acid as an efficient catalyst promoting the Dakin–West reaction at ambient temperature is reported for the first time in this paper. A few efficacious auxiliary catalysts were also developed for the Dakin–West reaction. A variety of substituted aryl aldehydes and aryl ketones were found to be applicable to the preparation of some new β-acetamido-β-arylpropiophenones. This procedure has several advantages such as high yields, short reaction time, and smaller amount (0.30 mol%) of catalyst.     

Radical polymerization of di-n-butyl itaconate in the presence of Lewis acids

Intramolecular chain-transfer reaction takes place in polymerizations of itaconates at high temperatures and/or at low monomer concentrations. Polymerizations of di-n-butyl itaconate (DBI) were carried out at 60 °C in the presence of Lewis acids such as scandium trifluoromethansulfonate. Lewis acids hardly influenced the intramolecular chain-transfer reaction in bulk polymerizations. Polymerizations in methanol accompanied transesterification reaction catalyzed by Lewis acids. In polymerizations in toluene, catalytic amounts of Lewis acids were found to be effective in suppressing the intramolecular chain-transfer reaction. Lewis acids showed no significant influences on stereospecificity of polymerization, though isotactic-specificity increase in polymerizations of other acrylate monomers such as methyl methacrylate.     

Microwave-Assisted Synthesis of 5′-O-methacryloylcytidine Using the Immobilized Lipase Novozym 435

Nucleobase building blocks have been demonstrated to be strong candidates when it comes to DNA/RNA-like materials by benefiting from hydrogen bond interactions as physical properties. Modifying at the 5′ position is the simplest way to develop nucleobase-based structures by transesterification using the lipase Novozym 435. Herein, we describe the optimization of the lipase-catalyzed synthesis of the monomer 5′-O-methacryloylcytidine with the assistance of microwave irradiation. Variable reaction parameters, such as enzyme concentration, molar ratio of the substrate, reaction temperature and reaction time, were investigated to find the optimum reaction condition in terms of obtaining the highest yield.     

Photosensitised oxidation of a water pollutant using sulphonated porphyrin

Photodegradation of endocrine disrupting butylparaben (BP) in aerated aqueous solutions was studied using 4,4′,4″,4‴-(porphine-5,10,15,20-tetrayl)tetrakis(benzenesulphonic acid) (TPPS₄), as a sensitiser. Influence of various parameters, such as initial sensitiser and BP concentration, pH of the reaction solution and oxygen content in the reaction solution, on the photosensitised oxidation was examined. It was found that the dominant pathway of BP degradation occurred in the reaction with molecular singlet oxygen ¹O₂, i.e. via photosensitised oxidation mechanism of type II. Kinetic parameters of the BP reaction with ¹O₂ were estimated.     

Reduction of nitrobenzene to aniline with carbon monoxide and water

Modified catalyst systems composed of palladium or its chloride and co-catalysts such as FeCl₃, Fe₂O₃, metallic Fe-powder, metallic Fe-wire net, iodine, pyridine or aniline, applied in the reduction of nitrobenzene to aniline in the presence of carbon monoxide and water are described. The reaction proceeds at 150–180 °C and 2.5–7 MPa gauge pressure. After 1–7 h the reaction was complete, reaching nitrobenzene conversions of 98–100%. Selectivity of the reaction with respect to aniline was also 100%.