Efficient synthesis of novel furo[2,3-d]pyrimidine derivatives under catalyst-free conditions

A series of furo[2,3-d]pyrimidine derivatives were synthesized via the [3+2] cyclization of pyrimidine-4,6-diol and a variety of nitroolefins at catalyst-free conditions. The reaction is easy to perform simply mixing inexpensive starting materials in water under conventional heating at 90 °C. The reaction proceeds at a fast speed within 1.5–2 h and gives the high biological and pharmacological active substituent furo[2,3-d]pyrimidine derivatives with good to high yields. Mechanism of formation of these furo[2,3-d]pyrimidine derivatives are also proposed.     

On the existence of temperature induced changes in the magnetic topology of crystals that show no first-order crystallographic phase transitions

The First-Principles Bottom–Up study of the 88 K and 273 K X-ray diffraction structures of the bis-2,3-dimethylpyridinium tetrabromocuprate molecular magnet shows that the analysis of the magnetic properties of a molecule-based magnet, that does not present any first order polymorphic transition in the range of temperature studied, depends on the X-ray structure employed. The reason is the thermal expansion anisotropy when the crystal goes from the low temperature phase to 273 K, which induces changes in the radical–radical J_AB interactions. As a consequence, the magnetic topology of the low temperature and 273 K structures change, a fact that induces a change in the macroscopic magnetic susceptibility curve (only the 88 K structure of bis-2,3-dimethylpyridinium tetrabromocuprate reproduces well the two-leg spin ladder experimental properties of this magnet). When anisotropic thermal effects are suspected one should use low temperature structures to study the magnetic properties at low temperature, and high temperature structures for the study of the magnetic properties in that range of temperatures.     

Enantio- and diastereoselective hetero-Diels–Alder reactions between 4-methyl-substituted Rawal’s diene and aldehydes catalyzed by chiral dirhodium(II) carboxamidates: catalytic asymmetric synthesis of (−)-cis-aerangis lactone

The first catalytic asymmetric hetero-Diels–Alder (HDA) reaction between 3-tert-butyldimethylsilyloxy-1-dimethylamino-1,3-pentadiene (4-methyl-substituted Rawal’s diene) and aldehydes is described. With 3 mol % of dirhodium(II) tetrakis[N-benzene-fused-phthaloyl-(S)-piperidinonate], Rh₂((S)-BPTPI)₄, the cycloaddition reaction proceeded exclusively in an endo fashion and gave, after a novel sequential treatment with dimethyl acetylenedicarboxylate and acetyl chloride, the corresponding 2,3-cis-disubstituted dihydropyranones with up to 98% ee and perfect diastereoselectivity. The utility of this catalytic protocol was demonstrated by an asymmetric synthesis of the (−)-cis-aerangis lactone.     

Radiation-induced degradation of aqueous 2,3-dihydroxynaphthalene

The degradation of aqueous 2,3-dihydroxynaphthaline (2,3-DHN) under the influence of γ-ray was investigated under various experimental conditions. Using 2.5×10⁻⁵ mol L⁻¹ 2,3-DHN in aerated media (pH=6–6.8) an initial degradation yield, G_i-(2,3-DHN)=0.32 was obtained, whereas in solutions saturated with N₂O the yield come to G_i-(2,3-DHN)=0.50.In airfree media the substrate decomposition was negligible. Possible reaction mechanisms are presented.Further, the rate constant, k(OH+2,3-DHN)=2.14×10¹⁰ L mol⁻¹ s⁻¹ was determined by competition reactions with PNDA.     

A novel tandem ene/Prins cyclization for the synthesis of octahydropyrano[2,3-c]pyrrole derivatives

A tandem ene/Prins cyclization of olefin tethered aldehyde with an aldehyde has been accomplished using 5 mol % scandium triflate at ambient temperature to afford a novel series of cis-fused octahydropyrano[2,3-c]pyrrole derivatives in good yields with high selectivity. This is the first report on a tandem cyclization of 4-methyl-N-(3-methylbut-2-enyl)-N-(2-oxoethyl)benzenesulfonamide with aldehydes.     

Novel chiral copper complexes of N,P-ferrocenyl ligands with central and planar chirality as efficient catalyst for asymmetric addition of diethylzinc to imines

A new type of chiral copper complexes of N,P-ferrocenyl ligands with central and planar chirality as efficient catalyst was applied to the enantioselective addition of diethylzinc to N-diphenylphosphinoylimines. The (R)- and (S)-enantiomers of the addition reaction were obtained for this transformation. In the presence of 6 mol % of bidentate ligand 1 and 12 mol % of Cu(OTf)₂, the asymmetric addition process affords N-diphenylphosphinoylamides in up to 97% ee and 95% yields.     

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.     

Regiospecific and diastereoselective aldol reaction of chiral N-sulfinyl metalloenamines with α,β-unsaturated trifluoromethyl ketones: Asymmetric synthesis of tertiary trifluoromethyl allylic carbinols

Regiospecific and diastereoselective aldol type reaction of chiral N-sulfinyl metalloenamines with α,β-unsaturated trifluoromethyl ketones was reported, which affords the corresponding tertiary trifluoromethyl allylic carbinols in high yields with good diastereoselectivities (dr up to 90:10). The reduction of the condensation product 3a with LiBHEt₃ and Catecholborane provides CF₃-substituted syn- and anti-1,3-amino alcohols 5a and 5b in high yields with excellent diastereoselectivities (dr > 99:1).     

Synthesis,crystal structure,and FET characteristics of thieno[2,3-b]thiophene-based bent-thienoacenes

Two novel bent-shaped thienoacenes, naphtho[2,3-b]naphtho[2′,3′:4,5]thieno[3,2-d]thiophene (bent-DNTT) and anthra[2,3-b]anthra[2′,3′:4,5]thieno[3,2-d]thiophene (bent-DATT) were synthesized from thieno[2,3-b]thiophene and their corresponding aromatic anhydrides by three steps: Friedel–Crafts acylation, acid-promoted cyclization, and reductive aromatization. The structural curvature improved the solubility of these thienoacenes in organic solvents. The bent-DNTT based FET device was fabricated by the spin-coating method. The device exhibited p-type characteristics with a mobility of 5.1 × 10^?5 cm² V^?1 s^?1. Its thin-film structure was fully characterized as an edge-on orientation with large intermolecular orbital coupling.     

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.     

Henry reaction catalyzed by recoverable enantioselective catalysts based on copper(II) complexes of α-methoxypoly(ethylene glycol)-b-poly(l-glutamic acid) and imidazolidine-4-one ligands

Herein we describe the preparation and characterization of a recoverable catalyst for a Henry reaction based on a Cu(II) complex of block copolymer α-methoxypoly(ethylene glycol)-b-poly(l-glutamic acid) with (2R,5S)- or (2S,5R)-5-isopropyl-5-methyl-2-(pyridine-2-yl)imidazolidine-4-one. The reactions of substituted aldehydes with nitromethane catalyzed by these catalysts proceed with high chemical yield (70–98%) and with high enantioselectivity (61–92% ee). The reaction mixture is in the form of a colloid system and is formed by self-organized aggregates of the catalysts with average hydrodynamic particle size of 189 ± 3 nm (DLS). After sevenfold recycling, the catalyst exhibited no decrease in the enantioselectivity and only a slight decrease (ca. 18%) in the yield for the Henry reaction of nitromethane with 2-methoxybenzaldehyde.     

New tetrahedral boron heterobicycles: Cyclocondensation of phenylboronic acid with β-keto butanoic acid N-acyl hydrazones

A series of 4-phenyl-2-aryl-8-methyl-6-oxo-7-phenylhydrazo-2H,4H,6H,7H,8H[1,3,4,2]-oxadiazaborolo[2,3-b][1,3,2]oxazaborines were prepared in high yields via the reaction of phenylboronic acid with various N-acylhydrazones of 3-keto-2-(2′-phenylhydrazono) butanoic acid in the presence of 4 Å molecular sieves. These derivatives represent a novel class of zwitterionic, tetrahedral boron heterocycles. Single crystal X-ray analysis of a representative boron containing product is reported.     

Synthesis of highly crystalline poly(dimethylbutadiene) (PDMB) by radiation-induced inclusion polymerization: A comparison with PDMBs synthesized by bulk and emulsion polymerization

Poly-2,3-dimethylbutadiene (DMBD) has been synthesized by the radiation-induced inclusion polymerization technique. 2,3-DMBD was included as a clathrate in the channels of thiourea crystals and polymerized with 300 kGy into a crystalline high trans-1,4-polydimethylbutadiene (PDMB) in high yield. For comparison 2,3-DMBD was also polymerized by bulk radiolysis in high vacuum at 150, 300 and 600 kGy. The resulting PDMB was obtained in very low yields and had a microstructure completely different from that observed on PDMB synthesized by inclusion polymerization and more similar to the structure of an emulsion-PDMB prepared by a free radical initiator. Trans-PDMB prepared by inclusion polymerization was characterized by a crystalline melting point at 272 °C.The radiation chemical yield for the PDMB obtained by inclusion polymerization was found G=212 monomer units (in PDMB)/100 eV. This value is 23.5 times higher that measured in PDMB prepared by bulk radiolysis of the monomer.     

Stereoselective synthesis of pseudoglycosides catalyzed by TeCl4 under mild conditions

Catalytic amounts of tellurium(IV) tetrachloride were used to promote the O-glycosylation of 3,4,6-tri-O-acetyl-d-glucal to give the corresponding 2,3-unsaturated-O-glycosides. With simple alcohols, the desired compounds were obtained in good yields and excellent anomeric selectivity in a short reaction time using only 2 mol % of the catalyst. The application of the method in the synthesis of a small set of glycopyranosides with rigid or flexible linkers gave the corresponding α anomers as products in good yields. Further applications of some of the synthesized compounds in allylation reaction of aldehydes gave the corresponding homoallylic alcohols in good yields.     

(Liquid + liquid) equilibrium data for the separation of 2,3-butanediol from aqueous streams using tetraoctyl ammonium 2-methyl-1-naphthoate

Microbiological production of 2,3-butanediol (2,3-BD) through fermentation using renewable feedstock is a promising option for the production of bio based chemicals. Liquid–liquid extraction could be a more efficient process, if a proper solvent is used. Tetraoctyl ammonium 2-methyl-1-naphthoate [TOA MNaph] is a tailor made hydrophobic ionic liquid that may be applied for the recovery of 2,3-BD from aqueous streams. In this work, the (liquid + liquid) equilibrium data for {2,3-BD + water + [TOA MNaph]} at (313.2, 333.2, and 353.2) K have been obtained and correlated to the NRTL and UNIQUAC activity coefficient models. Root square mean deviations (RMSD) values of 1.54% (NRTL) and 1.88% (UNIQUAC) were obtained, showing that both models can properly describe the experimental data. Compared to conventional solvents [TOA MNaph] presents a good balance between distribution coefficient (D_2,3BD = 1.08) and selectivity (S = 11.47).     

Synthesis of an antimetastatic tetrasaccharide β-D-Gal-(1→4)-β-d-GlcpNAc-(1→6)-α-D-Manp-(1→6)-β-D-Manp-OMe

An antimetastatic tetrasaccharide T₁,β-D-Gal-（1→4）-β-D-GlcpNAc-（1→6）-α-D-Manp-（1→6）-β-D-Manp-OMe,was synthesized with two approaches.The first approach was a conventional method employing thioglycoside and Koenigs-Knorr glycosylation reaction in 24%overall yield.The second one was a novel route through the azidoiodo-glycosylation strategy by using 2-iodo-2-deoxylactosyl azide as the donor in 36%overall yield.     

A novel C3-symmetric prolinol-squaramide catalyst for the asymmetric reduction of ketones by borane

A novel C₃-symmetric prolinol-squaramide has been developed for the asymmetric reduction of ketones by borane. By using only 5 mol % catalyst 1a for the reaction, high yields and excellent enantioselectivities (up to 95% yield, 93% ee) were obtained. Moreover, 1a can be easily recovered by simple precipitation and re-used for four cycles without losing the selectivity.     

Oxidative thermal degradation of LDPE and the determination of some thermodynamic quantities

The pyrolysis of polyolefin wastes is one of the possible ways to obtain chemical feedstocks. In this work, the thermal degradation of low density polyethylene, (LDPE), which is a major product within plastics, was investigated in a semi-batch reactor system. First-order rate kinetics approach was chosen and reaction rate coefficients, k, and some thermodynamic quantities determined such as activation energy, reaction enthalpy, free activation enthalpy, and entropy of degradation of LDPE for different air flow rates. We found that the maximum value of some thermodynamic quantities, such as reaction rate coefficient is 0.0243 min⁻¹ at 600 mL min⁻¹ air flow rate and the free activation enthalpy (ΔG^≠) is 148.66 kJ mol⁻¹ at 450 mL min⁻¹ air flow rate and the reaction enthalpy (ΔH^≠) is 57.65 J mol⁻¹ at 623 K temperature conditions. Moreover, we found that the oxidative degradation of LDPE is not spontaneous and has lower energy necessary (for degradation) than non-oxidative degradation processes.     

The chlorination kinetics of zirconium dioxide mixed with carbon black

In this research, the effects of chlorine gas at different chlorine partial pressures and carbon concentrations on the carbochlorination of zirconia were studied. It was found that in briquettes containing 18.7 %wt carbon, in a chlorine partial pressure range of 0.25–0.75 atm and for a reacted fraction of less than 0.7, the chemical reaction model was dominant for the carbochlorination process of zirconia. The order of reaction into chlorine gas (n) in this situation was 0.57. Moreover, the best weight ratio of carbon to zirconia was 40/60. In this case, the activation energy of the reaction was 209.9 kJ mol^?1 in a temperature range of 1023–1223 K, and the dominant model was the chemical reaction model.     

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.