Journal of Chemical Research

Protonation of the reactive 1:1 intermediate produced in the reaction between dialkyl acetylenedicarboxylates and triphenylphosphine by 3-(arylsulfonylhydrazono)butanoates leads to vinylphosphonium salts which undergo Michael addition with the conjugate base of the CH-acid to produce highly functionalised, salt-free phosphorus ylides in a diastereoselective manner and excellent yields.

The reactive 1:1 intermediates produced in the addition reactions between triethylamine and acetylenic esters were trapped by thiohydantoins to produce N-vinylthiohydantoins.

4-Benzyl-1-[(2E)-3-(3-bromo-4-hydroxy-5-methoxyphenyl)prop-2-enoyl]piperazine hydrochloride was prepared from 3-(3-bromo-4-acetyloxy-5-methoxyphenyl)-2-propenoic acid and benzylpiperazine. Its piperazine ring exhibits a chair conformation.

Ten novel methyl 3α-(4-nitrobenzoylhydrazides)-12α-(L-amino acid carbamates)-cholan-24-oate chiral molecular tweezers based on deoxycholic acid have been easily constructed using microwave irradiation. Their structures were characterised by IR, ¹H NMR, MS spectra and elemental analysis and their molecular recognition properties were investigated by UV-Vis spectral titration. The preliminary study indicated that these target compounds possess good selectivity for D/L amino acid methyl esters.

An environmentally friendly catalytic system of Fe₂(SO₄)₃/4-OH-TEMPO/NaNO₂ has been developed for aerobic oxidation of alcohols to aldehydes and ketones. The catalytic system allowed efficient and selective oxidation of a wide range of alcohols using oxygen at 1 atmospheric pressure and room temperature. 100% selectivity and excellent conversion rates were observed for benzylic alcohols and cinnamyl alcohol.

A four-component reaction between Meldrum's acid, aryl aldehydes with trialkyl phosphites in the presence of piper-idine has been developed. The reaction affords dialkyl {(aryl)[2,2-dimethyl-4-oxo-6-(piperidin-1-yl)-4H-[1,3]dioxin-5-yl]methyl}phosphonate in moderate to good yields in a one-pot process.

Two new polyhydroxypregnane glycosides, namely cynotophyllosides I-J, were isolated from the roots of Cynan-chum otophyllum, together with three known steroids, namely deacetylmetaplexigenin, sarcostin and hemoside. Their structures were established by extensive spectroscopic methods especially 2D NMR techniques) and acid-catalysed hydrolysis.

A new synthesis of the nonsteroidal anti-inflammatory drug tiaprofenic acid starting from thiophene is described. The sequence involves five steps, and the acylation with benzoyl chloride was catalysed by zinc oxide under solvent-free conditions at room temperature. This method uses a much cheaper starting material and has a higher total yield (78.4%) than other methods. It is suitable for industrial production.

A facile and efficient transition-metal-chloride/sodium-nitrite/TEMPO catalytic system for aerobic oxidative aromati-sation of Hantzsch 1,4-dihydropyridines in high yields under mild conditions is described.

Twelve new Schiff bases containing a disubstituted 1,2,4-triazole and a monosubstituted indole linked by a thioethyl group were efficiently synthesised via a method employing microwave irradiation. Compared with a conventional method of heating at 100 °C, yields were increased from 46–48 to 82–92% and the reaction times were reduced from 20–25 h to 4–7 min. The structures of these novel hexacyclic Schiff bases were characterised by their spectral data and elemental analysis. Evaluation of their antibacterial activity showed that many of them possess excellent activity against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Bacillus subtilis.

The regioselective Mitsunobu alkylation of saccharin with various alcohols has been examined. The N/O-alkylation is dependent on the steric hindrance of the alcohols, that is, less sterically hindered alcohol preferentially afford N-alkylated saccharin and vice versa.

Deprotection of phenylhydrazones and tosylhydrazones to their parent aldehydes and ketones has been accomplished using iodobenzene as catalyst in the presence of mCPBA as the terminal oxidant at room temperature. The reaction is general, and the target products can be obtained in good to excellent yields.

A facile method for solid-phase organic synthesis of 1-(E)-phenylethenyl-4-substituted-1,2,3-triazoles from polystyrene-supported (2-azido-1-phenyl)ethyl selenide and substituted ethynes has been developed. The advantages of this method include straightforward operation, high yield and purity of the products, as well as lack of odour and good stability of the polymeric reagent.

An improved synthesis of 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) is described, using N-nitroso-bis-(cyanomethyl)amine as the starting material in four steps including cyclisation, acidification; nitration and N-oxidation with a total yield of 54%. The factors influencing the reaction steps are discussed.

Oxidation of phenosafranin and an excess of aniline gave a novel hydroxylated derivative of pseudo-mauveine. N-Methyl-p-toluidine and bis(4-methylphenyl)amine are efficient building blocks for making mauveine-related chromophores. Their oxidation with K₂Cr₂O₇ is believed to form nitrogen centred radicals which then couple with an aromatic amine by homolytic aromatic substitution of hydrogen. The N-methyl substituent and the p-methyl sub-stituents are essential for the reaction to proceed. N-Methyl substituted chromophores were not demethylated in the reaction or by oxidation with K₂Cr₂O₇ in dilute H₂SO₄. N-Nitroso-bis(4-methylphenyl)amine rearranges smoothly to the orange compound, (2-nitro-4-methylphenyl)-4-methylphenylamine, when a solution in CH₂Cl₂ is treated with montmorillonite at room temperature for 24 h. 2,4-Dimethylaniline has been used to make a mauveine homologue. The colour of silk dyed with mauveine chromophores has been compared to the colour of silk dyed with authentic 1862 mauveine.

Diazo compounds derived from aromatic aldehydes were reacted with derivatives of (Z)-2-arylidene-2H-benzofuran-3-ones to give new highly substituted heterocyclic pyrazoles. The structures of the synthesised compounds were determined on the basis of their elemental analyses and spectroscopic data.

Synthesis of new substituted pyrazolo[4,3-f]thieno[3,2-b]quinoline-10-carbonitriles has been accomplished by the nucleophilic substitution of hydrogen in 5-nitroindazole derivatives. The synthesised compounds revealed fluorescent properties and the characteristics of the compounds were studied using UV absorption and emission spectroscopy.

(E)-2-[2-(4-bromothiophen-2-yl)vinyl]quinoline was prepared through an acid catalysed condensation of 2-meth-ylquinoline and 4-bromothiophene-2-carbaldehyde. Subsequent palladium-catalysed cross-coupling with various arylboronic acids gave a series of novel fluorescent thiophene and quinoline derivatives. The structures of the products were characterised using IR, ¹H NMR, ¹³C NMR, and elemental analysis. The UV-Vis absorption and photo-luminescence spectra of these derivatives were investigated.