Letters in Organic Chemistry - Volume 9, Issue 1, 2012

Letters in Organic Chemistry has completed 8 years of its existence. As it enters its 9th year, we must all try harder to improve standards and increase the number of high quality publications in this important journal. I would like to thank the Associate Editors, Regional Editors and Editorial Board Members for their constant guidance and support. I would also like to thank Ms. Anila Mufti, Ms. Huma Iftekhar and Mr. Farrukh Imran in Bentham Science Publishers for their constant support in this publication effort.

Etherfication products were obtained from sodium salts of p-toluenesulfonylhydrazones in alcohol solutions at reflux temperature on treatment with catalytic amounts of iron-copper nanoparticles, and silver nanoparticles, which were prepared from Camellia sinensis natural extracts.

The condensation reactions of alkyl isocyanides with 1,3-dimethylbarbituric acid and aryl carboxaldehydes to afford 6-(alkylamino)-5-(3-aryl)-1,3-dimethylfuro[2,3-d]pyrimidine-2,4(1H,3H)-dione, in excellent yields under neutral conditions, are reported.

An efficient green synthesis of 3,4-dihydropyrimidin-2-(1H)-ones/thiones (DHPMs) using MgO/ZrO2 as heterogeneous basic catalyst from an aldehyde, β-keto ester and urea/thiourea under solvent-free conditions is described. A variety of aldehydes were studied with β-keto ester and urea/thiourea giving good to excellent yield of corresponding 3,4-dihydropyrimidin-2-(1H)-ones/thiones. This protocol has advantage of excellent yield, reusability, inexpensive and short reaction time at room temperature. The synthesized catalyst can be reused up to 5 consecutive cycles without any decrease in the yield.

L-lysine was applied to the synthesis of 3-substituted coumarins through the condensation of various salicylaldehyde with reactive methylene compounds in water. In this work, waste minimization, catalyst recovery, simple operation and easier product work-up were achieved.

Ritter reaction was carried out efficiently in subcritical water with catalytic amount of trifluoromethanesulfonic acid. The amides were formed in good to excellent yields from secondary alcohols and tert-butanol with various nitriles.

A series of novel symmetric triazine hydrazones [N3C3(-OC6H4-p-C(CH3)=N-NH-C(O)-C6H4-p-X)3] (X = H, Br, Cl, F, OH, OCH3, CH3, NO2, NH2) were prepared in excellent yields by a three-fold condensation reaction of 2,4,6- tris(4-acetylphenoxy)-1,3,5-triazine with p-substituted benzoic acid hydrazides [NH2-NH-C(O)-C6H4-p-X]. The structures were confirmed by FT-IR, 1H, 13C, 2D-HMQC NMR and mass spectrometry (MALDI-TOF).

Loracarbef (HL), a second generation cephalosporin antibiotic, possesses various donor sites for interaction with transition metal ions such as Cu(II), Co(II), Fe(III) and Ru(III) to form complexes of the type [M(Cl)(HL)(H2O)]Cl (M: Cu(II), Co(II)] and [M(Cl)2(HL)(H2O)2]Cl (M: Fe(III), Ru(III)] with metal:ligand (M:L) molar ratio 1:1. These complexes were prepared and characterized by physicochemical and spectroscopic methods. UV-Vis, IR and mass spectra suggest that HL potentially acts as a bi-dentate ligand, with spectroscopic properties of these complexes changing in response to pH changes. The HL ligand and the resulting metal complexes gave intense emissions (δmax = 376 nm) upon irradiation by Ultra-Violet light. The photoluminescence quantum yields and long excited-state lifetimes of the ligand and its complexes were calculated. The HL ligand has a photoluminescence quantum yield of 52% and a long excited-state lifetime of 4.88 ns. The photoluminescence intensities and quantum yields of the metal complexes were dramatically reduced with respect to that of the HL ligand upon complexation with various metals. Also, the magnetic properties of the complexes were measured and the electrochemical behavior of these synthesized complexes was studied over a glassy carbon electrode in various buffer solutions using cyclic voltammetry. The peak current and peak potential of the complex depend on pH, initial potential, and scan rate. The complexes were screened for antibacterial activity against several bacteria and yeast, and results were compared with the activity of the uncomplexed antibiotic. The synthesized compounds were found to have remarkable bactericidal and fungicial properties. It is interesting that copper, iron and ruthenium complexes were very effective against all microorganisms.

Ultrasound-promoted synthesis of β-acetamido ketones catalyzed by cobalt sulfate heptahydrate via one-pot multi-component reaction coupling of aromatic aldehyde, acetophenone and acetyl chloride in acetonitrile was carried out in excellent yields at 25-28 °C, providing an efficient synthesis of these compounds. The use of ultrasound increased the rate of reactions compared with reactions under reflux condition.

New surfactant-type bifunctional thiourea organocatalysts 3 were synthesized. It was found that in the presence of 10 mol% PhCOOH, bifunctional thiourea bearing a long chain 3b in 10 mol% loading could smoothly catalyze the asymmetric Michael reaction of nitroalkenes 4 with cyclohexanone at room temperature in the presence of water, giving the desired adducts 5a-i in good yields (80 - 93%) with high diastereoselectivities (syn/anti = 95/5 - > 99/1) and enantioselectivities (up to 92% ee).

The purpose of this review is to discuss and summarize some of the interesting findings and applications of modified chitosan (MCS) and their derivatives in different areas of drug delivery. This review highlights the important applications of MCS in the design of various novel delivery systems like liposomes, microspheres, microcapsules, and nanoparticles. In addition to their well-known effects on drug solubility and dissolution, bioavailability, safety, and stability, their uses as recipients in drug formulation are also discussed. This review also focuses on various factors influencing inclusion complex formation because an understanding of the same is necessary for proper handling of these versatile materials. Some important considerations in selecting MCS in drug formulation such as their commercial availability, regulatory status, and patent status are also summarized.

The CuBr-catalyzed cross-coupling reaction of aryl iodides with B2pin2 in the absence of ligand has been developed for the preparation of arylboronates. The reaction was also suitable for the borylation of aryl bromides and benzyl halides, albeit in moderate yields.

We report on the synthesis and mesomorphic behaviour of a new series of non-symmetric liquid crystal dimers with long terminal chains containing 1,3,4-oxadiazole group and azobenzene group as the mesogenic units. These nonsymmetric liquid crystal dimers are evidenced to display monolayer smectic A phase. Microphase segregation and specific intermolecular interactions between the two different mesogenic units are the major driving forces for the formation of the monolayer smectic A structure.