Solid–liquid equilibria of acenaphthene with o-, m-, or p-dichlorobenzene

A differential scanning calorimetry (DSC) was used to determine binary solid–liquid equilibria (SLE) for acenaphthene  + o-dichlorobenzene, +m-dichlorobenzene, and +p-dichlorobenzene over the whole concentration range. It was found that all systems are simple eutectic systems. The eutectic point of the (acenaphthene + o-dichlorobenzene) system is at 254.95 K and 0.0334 mole fraction of acenaphthene, that of the (acenaphthene + m-dichlorobenzene) system at 246.15 K and 0.0460 mole fraction of acenaphthene and that of the (acenaphthene + p-dichlorobenzene) system at 307.75 K and 0.2940 mole fraction of acenaphthene. Furthermore, the activity coefficients of the components in the binary mixtures have been correlated by the Scatchard–Hildebrand expression with one adjustable parameter. This approach offers a useful procedure for estimating with good accuracy.     

Host compounds (+)-(2R,3R)-1,1,4,4-tetraphenylbutane-1,2,3,4-tetraol (TETROL) and (2R,3R)-(−)-2,3-dimethoxy-1,1,4,4-tetraphenylbutane-1,4-diol (DMT) with guests o-, m- and p- toluidine: A comparative investigation

In this work, we have compared the host abilities of closely related compounds (+)-(2R,3R)-1,1,4,4-tetraphenylbutane-1,2,3,4-tetraol (TETROL) and (2R,3R)-(?)-2,3-dimethoxy-1,1,4,4-tetraphenylbutane-1,4-diol (DMT) when these were recrystallized from single and mixed toluidine guests. Significant differences in host behaviour and selectivities were revealed and these were explained by means of single crystal diffraction experiments. Thermal analyses were used to determine the relative complex stabilities, and these data correlated exactly with the host selectivity orders for both TETROL and DMT.     

Formation of 2-arylindane-1,3-diones and 3-alkylphthalides from methyl o-[α-phenylsulfonyl]toluate

2-Aryl-1,3-indanedione and phthalide derivatives have attracted considerable interest due to their anticoagulant, parasiticidal and a range of biological activities. The synthesis of 2-aryl-1,3-indanedione by the condensation of the title sulfone with aryl aldehydes through an interesting pathway and a previously unreported approach to 3-alkylphthalide from C-alkylated derivatives of 1 under microwave and conventional heating conditions are described.     

Stereospecific interconversion of cis- and trans-γ,δ-epoxy α,β-unsaturated ester systems

The unprecedented, stereospecific interconversion of cis- and trans-γ,δ-epoxy α,β-unsaturated ester systems has been realized, which involves the palladium-catalyzed stereospecific alkoxy or hydroxy substitution reaction with double inversion of configuration at the γ-position as the key step. The new methodology is not only applicable to various disubstituted and trisubstituted epoxy unsaturated esters, but also these interconversions proceed with an extremely high degree of stereoselectivity and efficiency.     

Bromophilic substitution/carbophilic substitution cascade reactions of α,α-dibromo-2-methoxyacetophenone with C-, N- and O-nucleophiles

α,α-Dibromo-2-methoxyacetophenone reacts, under mild reaction conditions, with C-, N- and O-nucleophiles via a bromophilic substitution/protonation/carbophilic substitution cascade process to afford α-monosubstituted-2-methoxyacetophenones in moderate to good yield. The only exception from this reaction pathway is the reaction with the anion derived from malononitrile in which 2-aroyl-1,1,3,3-tetracyanopropene is obtained.     

Syntheses of β- and γ-fluorophenyl cis- and trans-α-methylene-γ-butyrolactones

Preparation of a series of cis-γ-fluorophenyl-β-phenyl-α-methylene-γ-butyrolactones is reported via ‘allylboration’ of fluorobenzaldehydes with (E)-methyl 3-phenyl-2-((4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)methyl)acrylate. The corresponding trans-γ-fluorophenyl lactones were prepared either (i) via ‘allylboration’ using the (Z)-reagents or (ii) via an indium triflate-mediated isomerization of the cis-products. The difficulty in isomerizing difluorinated cis-products confirms the probable intermediacy of carbocations. Finally, the synthesis of cis-β-fluorophenyl-γ-phenyl-α-methylene-γ-butyrolactones was achieved via an indium-catalyzed allylation–lactonization of aldehydes with (Z)-2-(bromomethyl)-3-(fluorophenyl)acrylates.     

Stereoselective synthesis of 1-O-β-feruloyl and 1-O-β-sinapoyl glucopyranoses

1-O-β-Feruloyl and 1-O-β-sinapoyl glucopyranoses are two common substrates for serine carboxypeptidase-like acyltransferases and serve as acyl donors in the biosynthesis of numerous secondary metabolites. In addition, they are involved in plant cell wall cross-linking and are also ideal substrates for studying the kinetics of lignification involving hydroxycinnamates. We report the first chemical (and multi-gram scale) synthesis of 1-O-β-feruloyl and 1-O-β-sinapoyl glucopyranoses.     

Synthesis of cis- and trans-(±)-3-mercaptoproline and pipecolic acid derivatives via thio-Michael addition

The reactivity of 2,3-dehydroproline and 2,3-dehydropipecolic acid methyl ester derivatives with S-nucleophiles in the thio-Michael addition reaction has been explored. The addition of triphenylmethanethiol and subsequent trityl cleavage led to the corresponding cis- and trans-(±)-3-mercaptoproline and pipecolic acid derivatives in good yields.     

Synthesis and characterization of Ru/Au,Pd/Au,Pd/2Au,Pt/2Au and Cu/2Au heterometallic complexes of cyclodiphosphazane cis-{(o-MeOC6H4O)P(μ-NBu)}2

Mononuclear complexes of cyclodiphosphazane with an uncoordinated phosphorus centre [RuCl₂(η⁶-cymene){l-κP}] (1a) (L = cis-{(o-MeOC₆H₄O)P(μ-N^tBu)}₂) and [PdCl₂(PEt₃){l-κP}] (1b) react with 1 equiv. of [AuCl(SMe₂)] to afford Ru^II/Au^I and Pd^II/Au^I heterodinuclear complexes [RuCl₂(η⁶-cymene){μ-l-κP,κP}AuCl] (2) and [PdCl₂(PEt₃){μ-l-κP,κP}AuCl] (3), respectively. Heterotrinuclear complexes [PdCl₂{μ-l-κP,κP}₂(AuCl)₂] (4), [PtCl₂{μ-l-κP,κP}₂(AuCl)₂] (5) and [CuI{μ-l-κP,κP}₂(AuCl)₂] (6) containing Pd^II/2Au^I, Pt^II/2Au^I and Cu^I/2Au^I metal centers have been synthesized from the reactions of trans-[PdCl₂{l-κP}₂] (1c), cis-[PtCl₂{l-κP}₂] (1d) and [CuI{{l-κP}₂] (1f) respectively, with 2 equiv. of [AuCl(SMe₂)]. Molecular structures of complexes 2, 3 and 4 were established by single crystal X-ray diffraction studies.     

Nucleophilic replacement of p-(1-chloro-2,2,2-trifluoroethyl)phenols: novel synthesis of β-trifluoromethyl-tyrosine

Three para-(1-chloro-2,2,2-trifluoroethyl)phenols 2a-c were prepared by selective α-chlorination of the corresponding alcohols 1a-c. Substitution of 2a by active methylene compound 4 proceeds smoothly in the presence of an appropriate base at room temperature, giving substituted products 5-9 in good yields. On the basis of this finding, both the important β-trifluoromethyl-tyrosine 15 and its derivatives have been successfully synthesized.     

Vapor–liquid equilibria and density measurement for binary mixtures of o-xylene + NMF, m-xylene + NMF and p-xylene + NMF at 333.15 K, 343.15 K and 353.15 K from 0 kPa to 101.3 kPa

Isothermal vapor–liquid equilibria at 333.15 K, 343.15 K and 353.15 K for three binary mixtures of o-xylene, m-xylene and p-xylene individually mixed with N-methylformamide (NMF), have been obtained at pressures ranged from 0 kPa to 101.3 kPa over the whole composition range. The Wilson, NRTL and UNIQUAC activity coefficient models have been employed to correlate experimental pressures and liquid mole fractions. The non-ideal behavior of the vapor phase has been considered by using the Peng–Robinson equation of state in calculating the vapor mole fraction. Liquid and vapor densities were measured by using two vibrating tube densitometers. The excess molar volumes of the liquid phase were also determined. Three systems of o-xylene + NMF, m-xylene + NMF and p-xylene + NMF mixtures present large positive deviations from the ideal solution and belong to endothermic mixings because their excess Gibbs energies are positive. Temperature dependent intermolecular parameters in the NRTL model correlation were finally obtained in this study.     

Synthesis of novel photolabile glycosides from methyl 4,6-O-(o-nitro)benzylidene-α-d-glycopyranosides

Novel photolabile sugar derivatives bearing a 4- or 6-O-(o-nitro)benzyl group have been prepared from the corresponding methyl 4,6-O-(o-nitro)benzylidene α-d-glycopyranosides. Regioselective cleavage with BF₃·Et₂O/Et₃SiH led to the methyl 6-O-(o-nitro)benzyl gluco- and manno-α-d-glycopyranosides 3 and 6. Inversion of configuration at 4-OH position of gluco and manno derivatives offered the otherwise inaccessible methyl 6-O-(o-nitro)benzyl galacto- and talo-α-d-glycopyranosides 4, 5, and 7. Careful reaction with PhBCl₂/Et₃SiH (3 equiv of reagents, 10 min at −78 °C) led to the desired methyl 4-O-(o-nitro)benzyl gluco- and manno-α-d-glycopyranosides 8 and 9 in very good yield. However, prolonged reaction with 6 equiv of PhBCl₂/Et₃SiH transformed the methyl 4,6-O-(o-nitro)benzylidene α-d-glucopyranoside 11 into the reduced d-glucitol derivative 15. Oxidative cleavage of 5,6-diol function of 15 gave the corresponding photolabile l-xylose 17. The photolabile glucosides 3 and 8 have been further transformed into the photolabile α-C-allyl d-glucopyranosides 20 and 22.     

A recyclable copper catalysis in quinoxaline synthesis from α-hydroxyketones and o-phenylenediamines

o-Phenylenediamines react with α-hydroxyketones in toluene at 100 °C in the presence of a catalytic amount of a copper catalyst along with MS 4A under O₂ atmosphere to afford the corresponding quinoxalines in high yields. The catalytic system could be easily recovered and reused several times without any loss of catalytic activity.     

Characterization of low molecular-weight gelator methyl-4,6-O-(p-nitrobenzylidene)-α-d-glucopyranoside hydrogels and water diffusion in their networks

This paper focuses on the thermal properties, the microstructure, and the molecular dynamics of water in the hydrogels (1.5, 2, 3, 4, and 5% [g mL⁻¹]) formed by sugar-based low molecular-weight gelator methyl-4,6-O-(p-nitrobenzylidene)-α-d-glucopyranoside. The energy needed to break the non-covalent interactions such as the hydrophobic, dipole-dipole, and π-π stacking interactions responsible for the gel formation was calculated to be 43 kJ mol⁻¹. The microstructure of the 4% [g mL⁻¹] hydrogel shows a characteristic fibril structure of the gel network with individual gel fibers, the junction points of thicker fibers, and pores occupied by water. The single mode diffusion of water molecules inside the gel network was detected irrespective of the diffusion time Δ (8-75 ms) and hydrogel concentration. For Δ of 10 ms the water diffusion is almost free and characterized by the diffusion coefficient in the range from 2.17×10⁻⁹ to 1.84×10⁻⁹ m² s⁻¹ for studied hydrogels. For larger Δ values, so-called restricted diffusions are observed and manifested in the linear decreases of the diffusion coefficient with diffusing time Δ, as shown for 5% gel. Only the one average proton spin-lattice relaxation time T₁ of water was determined for the studied hydrogels, irrespective of gelator concentration.     

Solid–liquid equilibria of the ternary system m-nitrobenzoic acid + p-nitrobenzoic acid + acetone

Solubility data and the density of equilibrium liquid phase for the ternary system m-nitrobenzoic acid + p-nitrobenzoic acid + acetone were determined at 283.1 K and 313.1 K, and the phase diagrams of the system were constructed. Two solid phases, pure solid m-nitrobenzoic acid and p-nitrobenzoic acid are confirmed by the Schreinemaker's wet residue method. The crystallization regions of m-nitrobenzoic acid and p-nitrobenzoic acid increase as the temperature decreases. At the same temperature, the crystallization region of p-nitrobenzoic acid is larger than that of m-nitrobenzoic acid.     

Total synthesis of (6Z,9S)-3,4-trans-9-hydroxy-3-methyldodec-cis-6-en-4-olide and (6Z)-3,4-trans-9-oxo-3-methyldodec-cis-6-en-4-olide γ-butyrolactones

The first total synthesis of (6Z,9S)-3,4-trans-9-hydroxy-3-methyldodec-cis-6-en-4-olide and (6Z)-3,4-trans-9-oxo-3-methyldodec-cis-6-en-4-olide was achieved in a convergent pathway. The salient features of our synthesis include Ohira–Bestmann reaction, regioselective alkyne addition to terminal epoxide, TEMPO/BAIB mediated oxidative lactonization, and partial hydrogenation.     

Synthesis and conformational studies of chiral meso-(α,β-unsaturated)-porphyrins

We describe a method to improve the yield and the kinetics of the difficult syntheses of α,β-unsaturated porphyrins, which enabled us to obtain a new chiral porphyrin derived from (S)-(−)-perillaldehyde in a 6% yield. Variable temperature NMR experiments on the free base, the zinc(II) and the nickel(II) complexes showed that two distinct and consecutive dynamic processes linked with the meso substituents rotation occurred. These processes can be analyzed as an evolution of the conformer composition upon temperature change. Higher values are found for the free energies of rotation of the substituent (measured by variable temperature ¹H NMR) compared to those of other equivalent porphyrins like meso-tetraphenyl porphyrin or meso-tetracyclohexyl porphyrin.     

Versatile synthesis of 4-spiro-β-lactam-3-carbonitriles via the intramolecular nucleophilic cyclization of N-(p-hydroxyphenyl)cyanoacetamides

A series of 4-spiro-cyclohexadienonyl-β-lactam-3-carbonitriles, 2,7-dioxo-1-azaspiro[3.5]nona-5,8-diene-3-carbonitriles, was synthesized in satisfactory to excellent yields via the intramolecular nucleophilic cyclization of N-(p-hydroxyphenyl)cyanoacetamides with iodobenzene diacetate (IBD) as oxidant and potassium hydroxide as base. Acetic 4-spiro-cyclohexadienonyl-β-lactam-3-carbimidic anhydrides were obtained when organic base triethylamine was applied instead of potassium hydroxide. The mechanisms of the intramolecular nucleophilic cyclization and formation of acetic β-lactam-3-carbimidic anhydrides were proposed. The cyclization is a sequence of nucleophilic ipso addition and oxidative dearomatization. The formation of acetic carbimidic anhydrides is an acid-catalyzed acetate addition to the nitriles.     

Flavonol 3-O-robinobiosides and 3-O-(2″-O-α-rhamnopyranosyl)-robinobiosides from Sesuvium portulacastrum

Six new flavonol 3-O-robinobiosides and 3-O-(2″-O-α-l-rhamnopyranosyl)-robinobiosides, sesuviosides A-F, were isolated from the aerial portion of Sesuvium portulacastrum together with ecdysterone, adenosine, 2′-O-methyladenosine, and l-tryptophan. The structure elucidations were based on analyses of chemical and spectroscopic data including 1D and 2D-NMR. Sesuviosides A-F and their aglycones exhibited radical scavenging activity using DPPH and ORAC assays.