Journal of Chemical Research

2-Diazopropane and diazo compounds derived from aromatic aldehydes were reacted with aromatic esters of 3-hydroxyprop-1-yne to give the aromatic esters of 5-hydroxymethyl-3-substituted pyrazoles. Anti-microbial screening using the Gram positive (Staphylococcus aureus and Enterococcus fecalis) and Gram negative (Escherichia coli and Klebsiella pneumoniae) bacteria and the yeast Candida albicans, showed that these compounds had promising activity against both Gram positive and Gram negative bacteria.

A convenient procedure for the synthesis of cyanohydrins by the addition of trimethylsilyl cyanide to aromatic aldehydes, heteroaromatic aldehydes, aliphatic aldehydes and unsaturated aldehydes catalysed by MgI₂ etherate (MgI₂·(OEt₂)_n) in good to excellent yields is described.

(Z)-α-Acyl-α,β-unsaturated esters can be stereoselectively synthesised in one pot under mild conditions and in good yields by the palladium-catalysed hydrostannylation of alkynyl esters in benzene, followed by the Stille cross-coupling with aryl acyl chlorides using CuI as co-catalyst.

Various substituted N-aryl carbamoyl methyl diacetates have been synthesized from N-aryl-3-oxobutanamides via a diacetoxylation mediated by the combination of iodobenzene diacetate (PIDA)/Zn(OAc)₂. This provides a new convenient method to form C–O bonds and cleave C–C bonds. Ten examples were obtained from easily available materials in good to excellent yields.

An efficient method for preparation of aryl nitriles is reported using Cu(I) to catalyse the reaction of aryl diazonium silica sulfates with sodium cyanide under mild conditions at room temperature in water. This method has the advantages of high yields, simple methodology, short reaction times and easy work-up.

Aldimines, generated in situ from 4-[2,2-bis(trimethylsilyl)ethenyl]benzaldehyde and aromatic amines, undergo Mannich-type reactions with cyclic and acyclic ketones. The one-pot reaction is efficiently catalysed by zirconium oxychloride (ZrOCl₂.8H₂O) at room temperature. β-Amino carbonyl compounds containing bis(trimethylsilyl)ethenyl groups are obtained in acceptable to good yields with moderate to high stereoselectivity under solvent-free conditions.

The synthesis of a novel series of 5-[(X-benzoylamino)]-1-(2,4-dinitrophenyl)-1H-4-pyrazolecarboxamide derivatives is described. Their antibacterial activity (MIC) against methicillin-susceptible and methicillin-resistant Staphylococcus aureus (MRSA) were determined. The results revealed that two of the compounds, X = 4-MeO and X = 4-NO₂, displayed greater antibacterial activity against MRSA than did cephalexin, cloxacillin and erythromycin.

A high yielding environmentally benign protocol has been developed for the synthesis of 3-(pyrrol-1-yl)-indolin-2-ones using a Lewis acid surfactant combined catalyst in water.

Two series of Schiff base dioxomolybdenum (VI) complexes of the general formula [MoO₂(L)(MeOH)] (L = D-glucosamine-derived Schiff base) have been synthesised, characterised and their asymmetric catalytic activities evaluated through the epoxidation of styrene. The molybdenum complexes with acetyl-protected D-glucosamine Schiff base ligands exhibited higher enanatioselectivity than those with unprotected sugar ligands. Protecting D-glucosamine by acetyl groups is an effective way to improve asymmetric catalytic epoxidation activities.

A novel turn-on fluorescent sensor based on a calix[4]arene with two coumarin units as fluorophores and iminogroups as ionophores on the upper rim has been synthesised. Its recognition properties towards heavy and transition metal ions have been studied by UV-Vis and fluorescence spectrometry. The compound showed an enhanced fluorescent intensity in the presence of Fe³⁺ or Cr³⁺ ion, a high selectivity to Fe³⁺ or Cr³⁺ ions and a complexation ratio towards Fe³⁺ or Cr³⁺ of 1:1. The association constant for Fe³⁺ was 5.37×10⁵ M⁻¹ and for Cr³⁺ was 9.18×10⁵ M⁻¹.

S-Alkylisothiosemicarbazone and imidazolidinone derivatives were synthesised from pyrazole 4-carbaldehyde in a one pot reaction. The synthesised compounds were characterized by IR, ¹H NMR, ¹³C NMR, mass and elemental analysis. Most of the synthesised compounds showed antimicrobial activity against S. Aureus, B. subtilis, E. coli, P. aeruginos, A. Niger and C. albicans.

Nucleophilic substitution of hydrogen in 5-nitrobenzimidazole derivatives occurs upon reaction with 4-methylbenzyl cyanide under basic conditions and proceeds with concomitant cyclisation. This sequence offers a one-pot synthesis of new fluorescent heterocyclic compounds, 3-alkyl-8-methyl-3H-imidazo[4,5-a]acridines.

Reaction of HgCl₂ with bis[4-(pyridine-2-yl)pyrimidin-2-ylthio]methane (2-bppt) gave [(HgCl₂)₂(HgCl₂)(2-bppt)]_n, which consists of a one-dimensional inorganic (HgCl₂)_n chain surrounded by 2-bppt bridging ligands.

A facile method for the regioselective Friedel–Crafts acylation of indoles with acyl chlorides catalysed by zinc oxide in an ionic liquid medium has been developed. The corresponding 3-acylindoles were obtained in good to high yields under mild reaction conditions. Zinc oxide, which is easily available and requires no special handling procedures, is an efficient catalyst for acylation of indoles.

In this study a mild, efficient and environmentally friendly method has been developed for the synthesis of amides and esters in the presence of hydrotalcite in water at room temperature. Different types of amines and phenols have been used and in all cases the products were obtained in moderate to high yields after an easy work-up. This method follows the principles of green chemistry.

The chiral Cd(II) complex {[Cd(L)(CH₃COO)₂(H₂O)]·H₂O} _n {L = 1,1′-[bis-3-(3-pyridyl)pyrazol-5-yl]ferrocene} has been synthesised. The Cd(II) ion is coordinated by two pyridyl nitrogen atoms, two chelating acetate anions and one water molecule, showing a distorted pentagonal-bipyramidal coordination environment. Each ligand L serves as a bisconnector, bridging two Cd atoms through its two pyridyl moieties, to afford an infinite 1D left-handed helical chain along the a-axis with a short pitch of 5.8761 (9) Å. Moreover, all of the left-handed helical chains are joined by hydrogen bonds to form a left-handed homochiral crystal.

Poly(4-vinylpyridine)-supported copper(I) iodide nanoparticles have been used as an efficient, green recyclable catalyst for the chemoselective synthesis of pentaerythritol diacetals from aromatic aldehydes and pentaerythritol under solvent-free conditions. This catalyst was reused six times without any loss of its activity.

A simple one-pot efficient method is described for the synthesis of 1,4-bis[thiazolo[4,5-d]pyrimidin-7(6H)-one] piperazine derivatives by a domino three-component process involving an aza-Wittig reaction/heterocyclisation in the presence of sodium ethoxide as catalyst. Ethyl 4-[(triphenylphosphanylidene)amino]-2,3-dihydro-3-phenyl-2-thioxothiazole-5-carboxylate reacted with aromatic isocyanates to give carbodiimide intermediates. This was followed by the addition of piperazines to give the corresponding guanidine intermediates. The guanidine intermediates were then cyclised in the presence of catalytic amount of sodium ethoxide to give 1,4-bis[thiazolo[4,5-d]pyrimidin-7(6H)-one]piperazine derivatives in good yields.

A series of new 3-arylazo-6-methyl-2,8,9-triphenyl-8H-imidazo[1,2-b]pyrazolo[4,3-d]pyridazines was prepared via reaction of hydrazonoyl halides with 3-hydrazonoacetyl-4-cyano-1,5-diphenylpyrazole. The structures of the compounds prepared were confirmed by spectral and elemental analyses. The solvatochromic and substituent effects on the absorption spectra of these azo dyes were interpreted by correlation of absorption frequencies with Kamlet–Taft and Hammett equations, respectively.

An efficient colorimetric anion sensor, N⁴-nitrophenylthiosemicarbazone of salicylaldehyde, behaves with a good selectivity and sensitivity in the recognition for F^- anions by naked eye observations and UV–Vis spectral changes in DMSO. The colour of the solution containing the sensor had an obvious change from colourless to purple only after the addition of F^- in DMSO while other anions did not cause obvious colour changes. The sensor reacted with F^- to form a stable complex and the association constant K_a is calculated as 1.415×10⁴ M⁻¹.