Microwave-assisted,mild, facile,and rapid one-pot three-component synthesis of some novel pyrano[2,3-d]pyrimidine-2,4,7-triones

Novel pyrano[2,3-d]pyrimidine-2,4,7-triones were synthesized in 90–97% yield via a three-component reaction of an aromatic aldehyde, Meldrums acid, and barbituric acid in the presence of 10 mol % K₂CO₃ under microwave irradiation. This is the first protocol to be reported for the synthesis of title compounds and the significant features of the present protocol are simplicity, high yields, short reaction time, involvement of aqueous work-up procedure, environmentally benign nature, and no chromatographic purification.     

Asymmetric Michael addition of aldehydes to nitroolefins catalyzed by a pyrrolidine–pyrazole

An effective protocol for the stereoselective Michael addition of aldehydes to nitroolefins using pyrrolidine–pyrazole as an organocatalyst is described. The catalytic cycle was found to be productive in terms of yield and selectivity, when performed under solvent-free reaction conditions and employing 15 mol % of catalyst and 10 mol % of benzoic acid at room temperature.     

Efficient dynamic kinetic resolution of secondary alcohols with a novel tetrafluorosuccinato ruthenium complex

Dynamic kinetic resolution (DKR) of a series of secondary alcohols has been conducted with a novel dinuclear ruthenium complex, bearing tetrafluorosuccinate and (rac)-BINAP ligands as the racemization catalyst. Novozym 435 has been used as the enzyme, and isopropyl butyrate as the acyl donor. Five substrates underwent DKR successfully: an aliphatic and an aromatic secondary alcohol, an aromatic alcohol with an electron-withdrawing substituent on the phenyl ring, an aromatic alcohol bearing an electron-donating substituent on the ring and a heteroaromatic secondary alcohol. The catalyst performed optimally at 70 °C. Typically the reaction reached complete conversion within 1 day with 0.1 mol % of racemization catalyst relative to the substrate. The addition of the ketone corresponding to the substrate stabilizes the active Ru complex and, therefore, increases the rate of the reaction.     

(Liquid + liquid) equilibrium for ternary mixtures of {heptane + aromatic compounds + [EMpy][ESO4]} at T = 298.15 K

(Liquid + liquid) equilibrium (LLE) data for the ternary systems (heptane + toluene + 1-ethyl-3-methylpyridinium ethylsulfate) and (heptane  + benzene + 1-ethyl-3-methylpyridinium ethylsulfate) were measured at T = 298.15 K and atmospheric pressure. The selectivity and aromatic distribution coefficients, calculated from the equilibrium data, were used to determine if this ionic liquid can be used as a potential extracting solvent for the separation of aromatic compounds from heptane. The consistency of tie-line data was ascertained by applying the Othmer–Tobias and Hand equations.     

Asymmetric nitroaldol reaction catalyzed by copper–diamine complexes: selective construction of two contiguous stereogenic centers

Chiral copper(II) complexes of secondary bisamines derived from 1,2-diaminocyclohexane were successfully used in the diastereoselective nitroaldol reaction. The reactions were carried out in the presence of 10 mol % of the Cu(II) complex and 7.7 mol % of i-Pr₂NEt in 2-propanol at ?30 °C. Good to excellent yields, enantioselectivities of up to 99%, and moderate to excellent diastereoselectivities were obtained for both aromatic or aliphatic aldehydes and various prochiral nitrocompounds forming the corresponding β-nitroalcohols with two contiguous stereocenters.     

Phase transitions on (liquid + liquid) equilibria for (water + 1-methylnaphthalene + light aromatic hydrocarbon) ternary systems at T = (563, 573, and 583) K

Phase transitions for (water + 1-methylnaphthalene + light aromatic hydrocarbon) ternary systems are observed at their (liquid + liquid) equilibria at T = (563, 573, and 583) K and (8.6 to 25.0) MPa. The phase transition pressures at T = (563, 573, and 583) K were measured for the five species of light aromatic hydrocarbons, o-, m-, p-xylenes, ethylbenzene, and mesitylene. The measurements of the phase transition pressures were carried out by changing the feed mole fraction of water and 1-methylnaphthalene in water free, respectively. Effects of the feed mole fraction of water on the phase transition pressures are very small. Increasing the feed mole fraction of 1-methylnaphthalene results in decreasing the phase transition pressures at constant temperature. The slopes depending on the feed mole fraction for 1-methylnaphthalene at the phase transition pressures are decreased with increasing temperature for (water + 1-methylnaphthalene + p-xylene), (water + 1-methylnaphthalene + o-xylene), and (water + 1-methylnaphthalene + mesitylene) systems. For xylene isomers, the highest and lowest of the phase transition pressures are obtained in the case of p- and o-xylenes, respectively. The phase transition pressures for ethylbenzene are lower than those in the case of p-xylene. The similar phase transition pressures are given for p-xylene and mesitylene.     

Preparation of various xanthene derivatives over sulfonic acid functionalized imidazolium salts (SAFIS) as novel,highly efficient and reusable catalysts

In this work, some novel sulfonic acid functionalized imidazolium salts (SAFIS), as a new category of ionic liquids, are synthesized by eco-friendly and simple procedures, and used as highly efficient and reusable catalysts to promote the following one-pot multicomponent organic transformations under solvent-free conditions: (i) the synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes from β-naphthol (2 eq.) and arylaldehydes (1 eq.), (ii) the preparation of tetrahydrobenzo[a]xanthene-11-ones from β-naphthol, arylaldehydes and dimedone, and (iii) the synthesis of 1,8-dioxo-octahydroxanthenes from dimedone (2 eq.) and aromatic aldehydes (1 eq.). Environmentally benign, simple methodologies, easy workup procedure, clean reaction, short reaction time, high yield and easy preparation of the catalysts are some advantages of this work.     

(Liquid + liquid) phase behavior for systems containing (aromatic + TBA + methylcyclohexane)

The determination region of solubility of TBA (tert-butanol) with representative compounds of the gasoline was investigated experimentally at temperature of 298.2 K. Type 1 (liquid + liquid) phase diagrams were obtained for (methylcyclohexane + TBA + aromatic compounds). These results were correlated simultaneously by the UNIQUAC model. The values of the interaction parameters between each pair of components in the systems were obtained for the UNIQUAC model using the experimental result. The root mean square deviation (RMSD) between the observed and calculated mole percents was 1.88 for (methylcyclohexane + TBA + benzene), 2.45 for (methylcyclohexane + TBA + toluene) and 2.86 for (methylcyclohexane + TBA + ethylbenzene). The mutual solubility of methylcyclohexane and aromatic compounds (e.g., benzene toluene and ethylbenzene (BTE)) was also investigated by the addition of TBA at temperature of 298.2 K.     

(Liquid + liquid) equilibria for ternary mixtures of (methanol or ethanol + toluene or m-xylene + n-dodecane)

(Liquid + liquid) equilibrium (LLE) results for the ternary mixtures of (methanol or ethanol + toluene or m-xylene + n-dodecane) at three temperatures (298.15, 303.15 and 313.15) K are reported. The compositions of liquid phases at equilibrium were determined by g.l.c. measurements and the results were correlated with the UNIQUAC and NRTL activity coefficient models. The partition coefficients and the selectivity factor of methanol and ethanol are calculated and compared to suggest which alcohol is more suitable for extracting the aromatic hydrocarbons (toluene or m-xylene) from n-dodecane. The phase diagrams for the ternary mixtures including both the experimental and correlated tie lines are presented. From the phase diagrams and the selectivity factors it is concluded that methanol has a higher efficiency as a solvent in extraction of aromatic hydrocarbon from alkane mixtures.     

(Liquid + liquid) equilibria in the binary systems (aliphatic,or aromatic hydrocarbons + 1-ethyl-3-methylimidazolium ethylsulfate,or 1-butyl-3-methylimidazolium methylsulfate ionic liquids)

(Liquid + liquid) equilibria of 14 binary systems composed of n-hexane, n-heptane, benzene, toluene, o-xylene, m-xylene, or p-xylene and 1-ethyl-3-methylimidazolium ethylsulfate, [emim]EtSO₄, or 1-butyl-3-methylimidazolium methylsulfate, [bmim]MeSO₄, ionic liquids have been done in the temperature range from (293.2 to 333.2) K. The solubility of aliphatic is less than those of the aromatic hydrocarbons. In particular, the solubility of hydrocarbons in both ionic liquids increases with the temperature in the order n-heptane < n-hexane < m-xylene < p-xylene < o-xylene < toluene < benzene. Considering the high solubility of aromatics and the low solubility of aliphatic hydrocarbons as well as totally immiscibility of the ionic liquids in all hydrocarbons, these new green solvents may be used as potentials extracting solvents for the separation of aromatic and aliphatic hydrocarbons.     

A mild robust generic protocol for the Suzuki reaction using an air stable catalyst

A mild but robust procedure has been developed as a first pass generic protocol for the Suzuki–Miyaura reaction. The protocol employs an air stable palladium pre-catalyst at low loading (≤1 mol %) in aqueous solvent mixtures at moderate temperature using potassium carbonate as base. Under these mild conditions, most aryl bromides will react with sterically and electronically demanding aryl boronic acids to give complete conversion to the product biphenyls in less than 1 h. Aryl chlorides are also fully converted in most cases either under identical conditions in 8–24 h, or in 2 h at elevated temperature. A further advantage of these mild conditions of moderate temperature, weak base and benign solvent is that sensitive functional groups and structural motifs are well tolerated. In addition, the lipophilic biphenyl products are readily isolated after a simple work-up procedure. These generic conditions are ideal for proof of transformation, and as the starting point for development and optimization of a specific process. The discovery and fine-tuning of this generic protocol will be presented, supported extensively by examples to illustrate its scope and utility.     

Phase equilibria study of the (N-octylisoquinolinium thiocyanate ionic liquid + aliphatic and aromatic hydrocarbon,or thiophene) binary systems

Binary liquid + liquid phase equilibria for 8 systems containing N-octylisoquinolinium thiocyanate, [C₈iQuin][SCN] and aliphatic hydrocarbon (n-hexane, n-heptane), cyclohexane, aromatic hydrocarbon (benzene, toluene, ethylbenzene, n-propylbenzene) and thiophene have been determined using dynamic method. The experiment was carried out from room temperature to the boiling-point of the solvent at atmospheric pressure. For the tested binary systems the mutual immiscibility with an upper critical solution temperature (UCST) for {IL + aliphatic hydrocarbon, or thiophene} were observed. The immiscibility gap with lower critical solution temperature (LCST) for the {IL + aromatic hydrocarbon} were determined. The parameters of the LLE correlation equation for the tested binary systems have been derived using NRTL equation. The phase equilibria diagrams presented in this paper are compared with literature data for the corresponding ionic liquids with N-alkylisoquinolinium, or N-alkylquinolinium cation and with thiocyanate – based ionic liquids. The influence of the ionic liquid structure on mutual solubility with aliphatic and aromatic hydrocarbons and thiophene is discussed.     

LLE data for the ionic liquid 3-methyl-N-butyl pyridinium dicyanamide with several aromatic and aliphatic hydrocarbons

(Liquid + liquid) equilibrium data for ternary systems of several aromatic and aliphatic hydrocarbons with the ionic liquid 3-methyl-N-butylpyridinium dicyanamide were determined at T = 303.15 K and 328.15 K and atmospheric pressure. As aromatics benzene, cumene and p-xylene have been chosen, as paraffins n-hexane and n-nonane were used. The experimental data were regressed and could be adequately correlated with the NRTL model. A logical order in the extraction capacity of 3-methyl-N-butylpyridinium dicyanamide for the different aromatics is obtained: benzene > p-xylene > cumene.     

Hole-transporting glass-forming indolo[3,2-b]carbazole-based diepoxy monomer and polymers

Hole-transporting indolo[3,2-b]carbazole-based diepoxy monomer and polymers are reported. The polymers were prepared by polyaddition reaction of indolo[3,2-b]carbazole diepoxide with aromatic dithiols in the presence of triethylamine. Their number average molecular weights range from 11500 to 14310 and polydispersity indices are in the range of 2.96–3.08. Thermal, optical, photophysical, electrochemical and photoelectrical properties of the title compounds were studied. Both the monomer, 5,11-di-2,3-epoxypropyl-6-pentyl-5,11-dihydroindolo[3,2-b]carbazole and the polymers were found to form glasses with the glass transition temperatures ranging from 37 °C for the monomer to 99 °C for one of the polymers. Time-of-flight hole drift mobilities observed in the solid amorphous films of the monomer exceeded 10^?4 cm² V^?1 s^?1 at an electric field of 10⁶ V cm^?1.     

Effective bioelectrocatalysis of bilirubin oxidase on electrochemically reduced graphene oxide

Graphene oxide (GO) was applied for construction of an effective biocathode based on bilirubin oxidase (BOD). Separation of small-sized GO sheets together with the BOD immobilisation protocol has detrimental effects on the bioelectrocatalytic reduction of oxygen. When BOD was deposited on electrochemically reduced GO (ErGO) only a negligible current density j = 2.6 μA cm^− 2 was observed. Current density dramatically increased to a value of 46 μA cm^− 2 once BOD was in-situ mixed with as-received GO directly on a glassy carbon electrode (GCE) with subsequent electrochemical reduction of the BOD/GO composite. When this protocol was tested with small-sized GO flakes separated simply using centrifugation, the fabricated biocathode exhibited j = 120 μA cm^− 2. A current density further increased to j = 280 μA cm^− 2 when BOD and purified GO were incubated ex-situ for 4 h, followed by the BOD/GO composite collection by centrifugation, its deposition on the GCE and electrochemical reduction. Moreover, oxygen reduction current increased steeply with a steady-state current density achieved at high potential (≈ 500 mV), close to the onset potential of oxygen reduction (≈ 580 mV).     

Structure characteristics contributing to flame retardancy in diazo modified novolac resins

The physical characteristics of two modified novolac resins (carbonyl phenyl azo novolac resin; CPAN and 4-(4-hydroxyphenyl azo) benzyl ester novolac resin; HPDEN) bearing nitrogen and aromatic functional groups by diazo-coupling or esterification in the branch structure of phenol novolac resin were examined. Presence of the modifiers raised the phenolic decomposition temperature (5% weight loss) from 300 °C (pure Phenolic) to 330 °C and 380 °C, while the char residue increased from 45% to 56% and 68%, respectively. The kinetics for thermal degradation energies (E_a) also rose from 151 kJ/mol K to 254 kJ/mol K (CPAN) and 273 kJ/mol K (HPDEN). The retarded decomposition kinetics is attributed both to the increase of crosslink densities and high aromatic content in the derivative resins. On the other hand, the diazo-coupling or phenyl diazenyl ester produces non-combustible gases (N₂, CO₂ and CO) during formation of aromatic char which dilute the ambient oxygen gas. Both the production of gases and the retarded kinetics due to cross-linking are definitive for the improved flame resistance.     

Use of selective ionic liquids and ionic liquid/salt mixtures as entrainer in a (vapor + liquid) system to separate n-heptane from toluene

During the last years, a large number of studies have evaluated the ability of ionic liquids (ILs) to separate aromatic from aliphatic hydrocarbons by liquid extraction. Nevertheless, in order to design a global process, a post-extraction step based on the aromatic recovery from the extract stream and the regeneration of the IL is required. Taking into account the negligible vapor pressure of the ILs, the use of separation units based on the difference of volatility among the components of the extract could be an appropriate way. However, that requires additional (vapor + liquid) equilibrium (VLE) data, which are scarce today. In this work, the isothermal VLE data for {n-heptane + toluene + 1-ethyl-3-methylimidazolium thiocyanate ([EMim][SCN])} and {n-heptane + toluene + 1-butyl-3-methylimidazolium thiocyanate ([BMim][SCN])} mixtures were experimentally measured at T = (323.2, 343.2 and 363.2) K over the whole composition range within the rich-IL miscibility region. For that, a static headspace gas chromatograph (HS-GC) was used. In addition, the non-random two liquids (NRTL) thermodynamic model was satisfactory applied to correlate the experimental VLE data.Finally, the effect of thiocyanate-based inorganic salts (AgSCN, Co(SCN)₂ and CuSCN) on the phase behavior of the above mentioned mixtures were also analyzed through the experimental determination of the isothermal VLE of the pseudo-ternary systems {n-heptane + toluene + [EMim][SCN]/salt mixture}.The obtained results show that the use of pure thiocyanate-based ILs as entrainer increases the n-heptane relative volatility from toluene whereas the addition of inorganic salts has not led to an improvement of these results.     

Non-isothermal decomposition kinetics,thermal behavior and computational detonation properties on 4-amino-1,2,4-triazol-5-one (ATO)

The thermal behavior of 4-amino-1,2,4-triazol-5-one (ATO) was studied under non-isothermal condition by DSC method in a sealed cell of stainless steel. The melting enthalpy and melting entropy of ATO are 21.34 ± 0.49 kJ mol⁻¹ and 46.54 ± 0.30 J mol⁻¹ K⁻¹, respectively. The kinetic parameters were obtained from the analysis of DSC curves by Kissinger method, Ozawa method, the differential method and the integral method. The main exothermic decomposition reaction mechanism of ATO is classified as nucleation and growth, and the kinetic parameters of the reaction are E_a = 119.50 kJ mol⁻¹ and A = 10^9.03 s⁻¹. The gas products and condensed phase products of the thermal decomposition of ATO were studied on two simultaneous devices of the fast thermolysis reaction cell (gas reaction cell) in situ in conjunction with rapid scan transform infrared spectroscopy (RSFT-IR) and the solid reaction cell in situ. The heat of formation (HOF) for ATO was evaluated by G3 theory. The detonation velocity (D) and detonation pressure (P) were estimated by using the well-known Kamlet–Jacobs equation, based on the theoretical HOF and the determined crystal density.     

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.     

One-pot efficient green synthesis of spirooxindole-annulated thiopyran derivatives via Knoevenagel condensation followed by Michael addition

A green, operationally simple and highly efficient one-pot three-component approach for the synthesis of spiro[indoline-3,4′-thiopyrano[2,3-b]indole] derivatives has been developed by the domino reaction of indoline-2-thione, isatin and ethyl cyanoacetate or malononitrile in ethanol at 80 °C for just 20 min. The significant advantages of this protocol are short reaction time, excellent yields, operational simplicity and formation of three new bonds in one operation from easily available starting materials.