Journal of Chemical Research

Ring-closing metathesis (RCM) and intramolecular Horner–Wadsworth–Emmons (HWE) reactions were assessed for synthesis of cis-5-methyl-6-phenylethyl-5,6-dihydro-α-pyrone. The RCM reaction employing Grubbs’ second generation catalyst afforded a 96% yield at 80 °C in toluene. The HWE reaction under modified Masamune–Roush conditions delivered only 23% yield due to a competitive elimination reaction.

The title compound, diethyl-2-[5-(4-fluorophenyl)-7-(trifluoromethyl)pyrazolo[1,5-a]pyrimidine-3-carboxamido]pentanedioate (C₂₃H₂₂F₄N₄O₅, Mr = 510.45) was synthesised and structurally characterised by element analysis, IR, ¹H NMR and single crystal X-ray diffraction. The crystal belongs to the monoclinic system, space group C₁₂₁ with a=27001(3) Å, b=7.161(1) Å, c = 12.0900 Å, α=90.00 °, β=92.379 (7) °, λ=90.00 °. In the crystal structure, the dihedral angles between the benzene ring and pyrazolopyrimidine are 53.618(162)°. Through C-H…F and C-H…O weak hydrogen bonds among molecules, the whole molecule is stacked into a three-dimensional structure. In addition, the compound possesses a moderate antituberculosis activity.

A novel copper-catalysed oxidative cyclisation has been developed for the synthesis of trisubstituted oxazoles, which is thought to proceed through cascade formation of C-N and C-O bonds by oxygen oxidation. The desired products can be obtained from readily available starting materials while avoiding hazardous materials. Therefore, a green synthetic method for the preparation of oxazoles has been found.

A two-step sequence was developed for synthesising different disubstituted 6,7-dichloro-1,2,3,4-tetrahydroquinoxalines without blocking the reactive centres. N-dichloroacetyl-6,7-dichloro-1,2,3,4-tetrahydroquinoxaline was prepared from 6,7-dichloro-1,2,3,4-tetrahydroquinoxaline and dichloroacetyl chloride giving N-acyl-N′-dichloroacetyl-6,7-dichloro-1,2,3,4-tetrahydroquinoxalines. The structures of all the compounds were characterised by IR, ¹H NMR, ¹³C NMR, and elemental analysis. The structure was determined by X-ray crystallography.

Complexes formulated as {[Ln(HPIDC)(μ₄-C₂O₄)_0.5(H₂O)]·2H₂O}_n [Ln=Sm or La; H₃PIDC=2-(pyridin-4-yl)-1H-imidazole-4,5-dicarboxylic acid] have been synthesised under hydrothermal conditions. The complexes are both built up from T-shaped 3-connected HPIDC^2- and 4-connected metal nodes and contain bridging oxalate (C₂O₄^2-) ligands, which might have been formed by the reductive coupling of CO₂ molecules released from the HPIDC^2- ligands through C-C bond cleavage.

A facile conversion of H-cardanol (side-chain hydrogenated cardanol, 3-pentadecylphenol; renewable fine chemical from the cashew industry) into value added 3-acylcoumarins, including those incorporating (+) menthol or cholesterol, has been achieved. The H-cardanol coumarin hybrid compounds were low melting, lipophilic and soluble in hydrocarbon solvents. They exhibit UV characteristics typical of 7-alkyl-3-acylcoumarins.

The enantiopure side-chain diester of homoharringtonine (HHT) has been prepared in 38% overall yield, from cheap L-aspartic acid by a linear sequence of 10 chemical operations (mean yield per step: 91%). The experimental operation in each step is convenient, economic and prone to scale up. About 7–10 g of the side-chain diester of HHT is easily prepared within one week from 5 g of L-aspartic acid.

2-Methyl and 2-cyanomethyl-12-aryl-8,12-dihydro-9H-chromeno[3,2-e][1,2,4]triazolo[1,5-c]pyrimidin-11(10H)-one derivatives were synthesised by the cyclisations of acetic anhydride or ethyl cyanoacetate with chromeno[2,3-d]pyrimidine derivatives, which were obtained by the reactions of hydrazine monohydrate and formimidate derivatives. In addition, 2,9,9-trimethyl-12-(p-tolyl)-8,12-dihydro-9H-chromeno[3,2-e][1,2,4]triazolo[1,5-c]pyrimidin-11(10H)-one and 2-cyanomethyl-12-phenyl-8,12-dihydro-9H-chromeno[3,2-e][1,2,4]triazolo[1,5-c]pyrimidin-11(10H)-one were further determined by single-crystal X-ray diffraction analysis.

Condensation of 4-(diethylamino)salicylaldehyde with aqueous hydrazine, followed by complexation with BF₃·OEt₂ gives a fluorescent indicator highly selective for copper. The indicator forms a 2 : 1 complex with Cu²⁺ and displays a highly sensitive and selective fluorescent quenching action with Cu²⁺ upon excitation at 440 nm in water/THF (7 : 3, v/v) solution. This action is pH-independent over the range 4.5 < pH < 9.5.

The mechanism of formation of a pyridin-2(1H)-one synthesised from vinamidinium salts and cyanoacetamide derivatives is illustrated through the preparation and characterisation of a key intermediate.

A selective mono-1,4-hydrocyanation of 10 diarenyl ketones using potassium hexacyanoferrate(II) as an eco-friendly cyanide source, potassium hydroxide as a catalyst, and benzoyl chloride as a promoter has been achieved. This protocol has the advantages of a non-toxic cyanide source, a heavy metal-free catalyst, selectivity, very good yields and a simple work-up procedure.

1,8-Di(quinol-2-yl)octa-1,7-diyne and 1,8-di(phenanthren-9-yl)octa-1,7-diyne were synthesised by conventional and microwave-assisted methods in good yields. Microwave irradiation enhances the rate of these reactions. Photophysical properties of these derivatives were also evaluated, and it was found that 1,8-di(phenanthren-9-yl)octa-1,7-diyne displays a higher fluorescence quantum yield than 1,8-di(quinol-2-yl)octa-1,7-diyne. The molecular structures of 1,8-di(quinol-2-yl)octa-1,7-diyne and 1,8-di(phenanthren-9-yl)octa-1,7-diyne were established by single-crystal X-ray diffraction studies.

Antimony (III) acetate was used in the one-pot three-component synthesis of biologically active 14-aryl-14H-dibenzo[a,j] xanthenes from the condensation between arylaldehydes and (3-naphthol under solvent-free conditions at ambient temperature. This methodology has a number of advantages such as, short reaction time, easy work-up and high yields.

Using an efficient and eco-friendly approach, 14 4-aryl-7,7-dimethyl-1,2,3,4,5,6,7,8-octahydroquinazolin-2,5-diones (and six of their 2-thione analogues) were prepared in good yields and in short reaction times by a three-component reaction of an araldehyde, dimedone and urea (or thiourea) using Fe₃O₄ nanoparticles in aqueous ethanol under reflux conditions. The Fe₃O₄ nanoparticles, which were easily prepared and could be recycled, were fully characterised by TEM, SEM, XRD, EDX, VSM and FTIR analysis.