Journal of Chemical Research

The efficient conversion of boronic acids, both arylboronic acids and alkylboronic acids, to the corresponding amines in water was accomplished in moderate to good yields using Cu(NO₃)₂ complexes of amines as the nitrogen source. The coupling reactions were performed in water at 30 °C for 2 hours.

Novel deoxycholic acid 3α-triazole conjugates based on methyl 3α-chloroacetoxy-12α-hydroxy-cholanate have been synthesised. The synthesis is accelerated by microwave irradiation under solvent free conditions in the presence of K₂CO₃. Some of these compounds were tested for antibacterial activity against B.subtilis, P.aeruginosa and S.aureus. The preliminary results indicated that these deoxycholic acid-triazole conjugates have good inhibitory effect against B.subtilis. All of the compounds were characterised by ¹H NMR, IR, ESI-MS spectra and elemental analyses.

The tri-nuclear cobalt(II) complex, [(CoL)₂(μ-OAc)₂Co]·2CHCl₃ (H₂L = 5,5'-dimethoxy-2,2'-[(ethylene)dioxybis(nitrilome thylidyne)]diphenol), has been synthesised. Its X-ray structure shows it to contain two acetate ions coordinating to the three cobalt(II) atoms through Co–O–C–O–Co bridges, and four μ-phenoxo-oxygen atoms from two [CoL] chelates also coordinating to the central cobalt(II) atom. The complex possesses two penta- and one hexa-coordinated cobalt atoms. The crystal packing of the Co^II complex shows that a 2D-layer supramolecular network parallel to the ab-plane is formed through intermolecular C–H···O and C–H···Cl hydrogen bonding interactions.

The reaction between dimedone, an aromatic aldehyde and urea catalysed by ZnO nanoparticles (ZnO NPs) in refluxing ethanol as a solvent provided a simple and efficient one-pot route for the synthesis of octahydroquinazolinone derivatives in excellent yields.

A number of β-hydroxy-ketone derivatives bearing a coumarin unit have been synthesised by the Reformatsky reaction of formyl coumarin and α-bromoacetophenone in an ionic liquid (1-butyl-3-methylimidazolium chloride, [Bmim]Cl). The recovered ionic liquid can be reused at least five times without a significant reduction in yield. This procedure is green, mild and environmentally benign.

An efficient synthesis of β-azido alcohols and β-hydroxy thiocyanates has been achieved by ring opening of epoxides using 1,1'-bis-methyl-3, 3-methylene-bisimidazolium dichloride as a phase transfer catalyst at room temperature in water. The reaction is regioselective and afforded the corresponding products in moderate to excellent yields.

An efficient and environment-friendly method for the synthesis of 1,3-oxazine derivatives has been developed using the ultrasound-mediated condensation of 2-naphthol with formaldehyde and primary amines under solvent-free condition at room temperature in the presence of BF₃-SiO₂ to give the desired product in good to excellent yield. This procedure provides several advantages over current methods including a simple work-up, cost effectiveness, a reusable catalyst and shorter reaction times.

Mono-, di-, tri- and tetra-O-arylmethyl-p-t-butylcalix[4]arenes were synthesised respectively from p-t-butylcalix[4]arene and arylmethyl bromide through an easy and selective one-step reaction. Mono- and di-arylmethyl ethers of p-t-butylcalix[4]arenes were prepared using LiH as a base, while tri- and tetra-arylmethyl derivatives were afforded in the presence of Ba(OH)₂ and BaO. These methods are remarkable for excellent selectivity, mild reaction conditions, moderate to good yields and easy purification.

The palladium acetate-catalysed dehalogenation of biaryl halides has been investigated in room temperature ionic liquids with pyridine acting as a co-solvent. The significant effect of pyridine in conjunction with Pd(OAc)₂ in [bmim][PF₆] gave excellent results in the dehalogenation of biaryl iodines and bromides. The pyridine activated the C2-H of the imidazolium salt to be the source of hydrogen. The separation of desired product was easily performed by extraction with diethyl ether and the Pd(OAc)₂–[bmim][PF₆] system could be recycled five times with only a small decrease in activity. This procedure represents an environmentally friendly method for the preparation of biaryl compounds without the use of complex ligands.

A two-step facile process for the preparation of 2,4-dichloro-3-cyano-5-fluorobenzoic acid, starting from easily available 2,6-dichloro-3-fluorobenzonitrile, has been developed. The overall yield was 58%.

The Cu(II) complexes, [Cu(2,5-pydc)(bmi)(H₂O)]_n, [Cu₂(H₂O)₂(2,6-pydc)₂(btx)]·2H₂O and [Cu(btc)₂(bmi)₂]·1.5H₂O, (bmi = 1-[(benzotriazol-yl)methyl)-1H-1,3-imidazole; 2,5-H₂pydc = pyridine-2,5-dicarboxylic acid; btx = 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene; H₃btc = 1,3,5-benzenetricarboxylate) have been synthesised and their X-ray structures show that hydrogen bonds and π···π stacking interactions are employed in their construction. The complexes can effectively catalyse the oxidative coupling reaction of 2,6-di-tert-butylphenol in good yield and unique selectivity.

The efficient and recyclable system, DMAP-based ionic liquid/water, has been developed and used in the Morita– Baylis–Hillman reaction of aromatic aldehydes with acrylates. The coupling reactions under the described basic reaction conditions proceed quickly with good to excellent yields. The ionic liquid could be reused at least five times without significant loss of activity.

A one-pot reaction of arylisoselenocyanates, hydrazine and bis(trichloromethyl) carbonate, in the presence of a base provides an efficient route for the synthesis of 5-arylamino-1,3,4-selenadiazol-2(3H)-ones in good to excellent yields. A plausible mechanism is proposed for the reaction.

Four unsymmetrical, salicylaldimine bis-Schiff bases with pendant benzo-10-aza-15-crown-5- or morpholino-groups and their 1:1 (ligand /metal) complexes with cobalt, copper and manganese have been synthesised and studied as catalysts in the aerobic oxidation of p-xylene to p-toluic acid. Significant selectivity (up to −90%) and conversion levels (up to −70%) were obtained. The effects of the pendant aza-crown ether group in Mn(III) Schiff base complexes on the oxidation of p-xylene were also investigated by comparison with analogues having pendant morpholino-groups.

Non-hygroscopic polystyrene-supported chloroaluminate ionic liquid was prepared from the reaction of Merrifield resin with pyridine followed by reaction with aluminium chloride. This Lewis acidic ionic liquid is an environmentally friendly heterogeneous catalyst for the Knoevenagel condensation of aromatic and aliphatic aldehydes with ethyl cyanoacetate. The catalyst is stable (as a bench top catalyst) and can be easily recovered and reused without appreciable change in its efficiency.

A simple, efficient, and high yielding one-pot protocol for the synthesis of novel highly substituted α-acyloxycarbox-amidobarbiturates has been developed by a three-component reaction of alloxans, various carboxylic acids, and alkyl or aryl isocyanides in acetonitrile at room temperature.

An effective and promising Ni/Cu catalytic system for the coupling of aryl iodides with various terminal alkynes has been developed. For the first time the readily available chiral amino alcohol has been employed as the ligand for the Pd-free Sonogashira coupling reaction.