Journal of Chemical Research

A new friedelane type triterpene, 3,16-dioxo-12α-hydroxyfriedelane was isolated from the chloroform extract of branches of Maytenus gonoclada Martius (Celastraceae) together with nine known compounds: 3, 11-dioxofriedelane, 3, 16-dioxofriedelane, 3, 12-dioxofriedelane, 3-oxo-12α,29-dihydroxyfriedelane, 3-oxofriedelane (friedelin), 3β-hydroxyfriedelane, 3-oxo-12α-hydroxyfriedelane and 3β-hydroxylup-20(29)-ene (lupeol) and a mixture of long chain hydrocarbons. The structure and stereochemistry of the new friedelane triterpene were established from the ¹H NMR and ¹³C NMR spectra including two-dimensional experiments (HSQC, HMBC and NOESY) and high resolution mass spectrometry.

A simple synthesis of 1,2,3,4-tetrasubstituted pyrrole derivatives from the reaction of enaminones with β-nitrosty-renes, under solvent-free conditions, is described.

An efficient synthesis of trialkyl 2-(dialkoxyphosphoryl)ethene-1,1,2-tricarboxylates is described. This involves the reaction of alkyl cyanoformates, dialkyl acetylenedicarboxylates, and trialkyl phosphites.

The reaction of dialkyl acetylenedicarboxylates with the N–H acid 4-phenyl-[1,2,4]triazolidine-3,5-dione in the presence of trialkyl(aryl) phosphites at reflux temperature led to the title phosphonato ester derivatives. The configurations of the compounds were determined (2R^*, 3S^* and mirror image) using the coupling constants and the Karplus equation.

Zinc-mediated addition reactions of propargyl bromide with a variety of aldimines afforded the corresponding homopropargyl amines under solvent-free conditions. The methodology is solvent-free, catalyst-free and involves a short reaction time (5 minutes).

The first crystalline TPPS complex [Zn(en)TPPS][Zn(en)₃] (where en is ethylenediamine and TPPS is tetraphenylporphyrin tetrasulfonic acid) has been synthesised via a solvothermal reaction and structurally characterised by a single-crystal X-ray diffraction. Zn(en)TPPS][Zn(en)₃ has discrete [Zn(en)TPPS]^2– and [Zn(en)₃]²⁺ moieties, which are interconnected via hydrogen bonds to form a three-dimensional supramolecular framework that possesses a large void space (1507.6 ų) corresponding to 22.5% of the unit-cell volume. The UV-Vis spectrum and photoluminescence have also been studied in detail.

The synthesis of (E)-2-(4-bromostyryl)quinoline involves an acid catalysed condensation of 2-methylquinoline and 4-bromobenzaldehyde. (E)-4′-[(2-(Quinolin-2-yl)vinyl)]-(1,1′-biphenyl)-4-carbaldehyde has been synthesised from (E)-2-(4-bromostyryl)quinoline and 4-formylphenylboronic acid via a Suzuki coupling reaction. A series of novel quinoline derivatives containing both a biphenyl group and an α, β-diarylacrylonitrile unit have been prepared by the base-catalysed condensation between (E)-4′-[(2-(quinolin-2-yl)vinyl)]-(1,1′-biphenyl)-4-carbaldehyde and various arylacetonitriles. By contrast, the acid-catalysed condensation of the latter aldehyde with several aniline derivatives has been used to synthesise quinolines containing an imine group. These compounds, which have implications for the manufacture of organic light-emitting diodes, emit blue to green fluorescence with maximum emission peaks of 419–531 nm in solution and in the solid state under UV irradiation. Thermogravimetric analysis reveals their good thermal stability with a decomposition temperature range from 313 to 387°C.

4-Bromothiophene-2-carbaldehyde was reacted with benzyl cyanide to prepare (Z)-3-(4-bromothiophen-2-yl)-2-phen-ylacrylonitrile which was cross-coupled with various arylboronic acids under Pd(PPh₃)₄ catalysis to afford a series of novel fluorescent aryl-substituted thiophene derivatives. These compounds are one of the most promising functional organic light-emitting diode materials. The UV-Vis absorption and photoluminescent spectra of these compounds in CH₂Cl₂ were investigated.

Cyclopropanes are important synthetic targets and intermediates. A series of L-proline derivatives as chiral ligands for the cyclopropanation reaction are reported here. The enantioselective cyclopropanation of cinnamyl alcohol has been accomplished with diethyl zinc and diiodomethane in the presence of chiral sulfonamides derived from L-proline and L-proline esters.

A series of chromen-2-one derivatives was synthesised by the reaction of 4-hydroxy-6-methyl-2H-pyran-2-one with substituted 2-hydroxybenzaldehydes catalysed by L-proline. This protocol has the advantages of easy workup mild reaction conditions and high yields.

Twelve novel amide type molecular tweezer anion receptors based on phenyl-1, 4-dioxyacetic acid have been synthesised using microwave irradiation. Their structures were established by ¹H NMR, IR, MS spectra and elemental analysis. Their binding properties were examined by UV-Vis spectra titration. The preliminary results indicate that these molecular tweezers show good recognition properties for Cl^-, Br^-, I^-, CH₃COO^-.

The reaction of (Z)-2-amino-N‘-arylbenzamidines with both 2,3-dichloro-5,6-dicyano-1,4-benzoquinone and 2,3,5,6-tetrachloro-1,4-benzoquinone have been studied. The reactions were carried at room temperature overnight in dry ethyl acetate and proceed via a charge transfer complexe to give dibenzo[b,e][1,4]diazepine derivatives in 35–44% yield. Benzodiazepine derivatives have anti-inflammatory, antiviral, antimicrobial, antileukaemic, antiplatelet, anticonvulsant, antianxiety, antidepressive and antitumour activities. The products were fully characterised according to their spectral analyses.

Star-shaped conjugated oligomers have many applications in materials science. Two new pseudo-C₃-symmetric star-shaped conjugated molecules 2,4,6-tris(4-styrylphenyl)pyridine and 2,4,6-tris(4-((E)-2-(thiophen-2-yl)vinyl)phenyl) pyridine have been synthesised and their structures characterised by ¹H NMR, ¹³C NMR, mass spectrometry and elemental analysis. UV-Vis and fluorescence spectrum show that the maximum absorption wavelengths are at 336 nm for 2,4,6-tris(4-styrylphenyl)pyridine and 356 nm for 2,4,6-tris(4-((E)-2-(thiophen-2-yl)vinyl)phenyl)pyridine, and the maximum emission wavelengths were at 398 nm and 408 nm respectively.

Isoxazoles have significant hypoglycaemic, immunosuppressive, anti-inflammatory, and anti-bacterial activities. A convenient high yielding procedure for the one-pot synthesis of 3-methyl-4-arylmethylene-isoxazol-5(4H)-ones by the condensation of ethyl acetoacetate, hydroxylamine hydrochloride and aromatic aldehydes in the presence of sodium silicate pentahydrate as an efficient catalyst in water at room temperature is described.

4-[4-(3-pyridinyl)imidazol-1-yl]-1-butylamine, the side chain of telithromycin, is used for the synthesis of novel ketolide antibiotics. The key step in synthesising 4-[4-(3-pyridinyl)imidazol-1-yl]-1-butylamine involves the HBr-induced DMSO oxidation of 3-acetylpyridine to 3-pyridylglyoxal, which was not isolated but transformed directly into 4-(3-pyridyl)imidazole by a Debus reaction with ammonia and formaldehyde.

An efficient oxidative esterification of aromatic and aliphatic aldehydes with simple alcohols was accomplished using catalytic amounts of 1,8-diazabicyclo[5.4.0] undec-7-ene (DBU) hydrobromide-perbromide as an oxidant in dichloremethane.

Quinoxaline derivatives are widely used in dyes, electroluminescent materials and organic semiconductors. An economic and convenient strategy for the synthesis of 2-phenyl-quinoxaline is described. The approach relies on the oxidation of acetophenones by [hydroxy(tosyloxy)iodo]benzene, followed by tandem nucleophilic substitution with o-phenylenediamines, dehydration cyclisation and dehydrogenation. The method was performed in two stages as a one-pot reaction.

N-heterocyclic carbenes have been successfully used as ligands in organometallic catalysis, and also as organocatalysts in different reactions. A series of novel chiral unsymmetrical imidazolinium salts which are precursors of N-heterocylic carbenes were synthesised effectively from the relatively inexpensive amino acid L-phenylalanine in six steps. These chiral unsymmetrical imidazolinium bromides were fully characterised by NMR and elemental analysis, and their specific rotations were obtained.

A variety of aromatic and aliphatic aldehydes can be easily converted into the corresponding cyclic and acyclic dithioacetals in the presence of MCM-41-supported mercapto ruthenium complex (MCM-41-SH-RuCl₃) in acetonitrile. This supported ruthenium complex can be recovered by simple filtration and reused several times without noticeable loss of activity.