Journal of the Iranian Chemical Society
Volume:4 Issue: 2, June 2007

This review article summarizes published data on the application of N-halo reagents (such as N-halo amines, N-halo amides and/or imides, N-halo sulfonamides and/or imides, and etc.) in various organic functional group transformations such as: oxidation reactions, deprotection and protection of different functional groups, halogenation of saturated and unsaturated compounds, acylation of alcohols, phenols, amines or thiols, epoxidation of alkenes, aziridination and etc. The main purpose of writing this review is encouraging of active researchers interested to this field for the synthesis of new N-halo reagents specially with different halogens and applications of these new N-halo reagents in organic reactions or finding more and more applications of existing N-halo reagents in organic synthesis.

Three new flavonol C-glycosides: 3′-(3″,7″-dimethyl-2″,6″-octadiene)-8-C-β-D-glucosyl- kaempferol 3-O-β-D-glucoside (1), 3′-(3″,7″-dimethyl-2″,6″-octadiene)-8-C-β-D- glucosyl-kaempferol 3-O-β-D-glucosyl [1→4]-α-D-glucoside (2) and 6-(3″-methyl-2″-butene)-3′-methoxyl-8-C-β-D-glucosyl-kaempferol 3-O-β-D-glucosyl [1→4]-β-D-glucoside (3) have been isolated from 80% ethanolic extract of the aerial parts of Sida cordifolia Linn followed by partitioning with ethyl acetate. Structures were established by chemical and spectroscopic methods.

The effects of the structural features of some 4,5-dichloroimidazolyl-1,4-dihydropyridine on their calcium channel antagonist activity have been studied using molecular modeling and quantitative structure activity-relationship analysis. Both symmetrical and asymmetrical dihydropyridine derivatives were used. AM1 semi-empirical quantum chemical calculation was used to find the optimum 3-D geometry of the molecules. Four different sets of descriptors, including chemical, topological, quantum chemical and substituent constant, were then calculated for each molecule. For each set of descriptors, the best multilinear QSAR equations were obtained by the stepwise variable selection method using leave-one-out cross-validation as selection criterion. Separate QSAR models were first obtained for symmetrical and asymmetrical derivatives, after which a general model was proposed for the entire set of molecules. This model has root mean square error of 0.45 and reproduces more than 82% of the variances in the calcium channel antagonist activity data. The sum of the negative charges, the energy of the highest occupied molecular orbital, molecular volume and the least negative charge were identified as the most significant descriptors.

A one-pot high yielding reductive amination of aldehydes with primary and secondary amines using LiClO4/NaBH4 and LiClO4/LiAlH4 as reducing agents in diethyl ether is described.

Tertiary, secondary, and benzylic alcohols react efficiently with nitriles in the presence of the catalyst calcium hydrogen sulfate, Ca(HSO4)2, to produce amides in high yields. In this study, a modified Ritter reaction using this solid acid catalyst is found to be an environmentally safe method for converting 2,6-bis(hydroxymethyl)-4-halo anisole into the corresponding diamides in CH3CN.

The extraction of geniposidic acid and geniposide from Eucommia ulmoides was carried out by Soxhlet extraction, enzyme-assisted aqueous extraction, semi-bionic extraction and supercritical fluid extraction techniques and the extracts were analyzed by high performance liquid chromatography. The results showed that the best methods for extraction of geniposidic acid and geniposide are enzyme-assisted aqueous extraction and semi-bionic extraction. Compared with various extraction methods, the semi-bionic extraction was more efficient, yielding the highest amount of geniposidic acid and geniposide. In semi-bionic extraction, no organic solvent was used. Semi-bionic extraction was performed at the same pH as that of the human body. The results indicated that semi-bionic extraction was the best method for large-scale efficient extraction of geniposidic acid and geniposide from plant materials. The supercritical fluid extraction process required more time than the other methods, and gave the lowest yields of geniposidic acid and geniposide.

The electrochemical properties of vanadyl(IV) derivatives, namely salen Schiff base complexes of the type [VO(Salen)] (5-BrSalen, 5-NO2Salen, 5-MeOSalen, salpn (bis(salicylaldehyde)-1,3-propanediamine, 5-BrSalpn, 5-NO2Salpn, 5-MeOSalpn, Me2Salen, Salophen, 5-BrSalophen, and 5-MeOSalophen) were investigated. The equatorial Schiff base ligands affect the oxidation potentials via interaction with the d-orbitals of the vanadyl metal ion. The cathodic peak potential (Epc) becomes less negative according to the sequence MeO- < H- < Br- < NO2-.

Electrochemical characterization and application of nickel ruthenium dioxide (Ni-RuO2) as a pH sensor for the determination of petroleum oil acid number is described. The sensor consists of RuCl3 thermally decomposed onto the upper side of a polycrystalline nickel electrode at 400 °C in an open furnace. The advantages of the sensor are: (i) easy preparation, (ii) fast response in a large pH range, (iii) high physical and chemical stability, and (iv) excellent reproducibility as determined by the reproducible linear variation of charge transfer resistance (Rct) as a function of overpotential (h) obtained by electrochemical impedance spectroscopy (EIS), and the Nernstian slope of the electrode potential in a wide range of pH (1.5-12.5) obtained by potentiometric measurements. The potentiometric selectivity coefficients of the sensor toward some anions and cations were evaluated in aqueous solution. The characterized Ni-RuO2 pH sensor was successfully tested for the determination of petroleum oil acid number.

An efficient, clean and simple procedure for the Michael addition of phthalimide and saccharin to various α,β-unsaturated esters in the presence of tetrabutylammonium bromide (TBAB) and 1,4-diazabicyclo[2,2,2]octane (DABCO) under solvent-free conditions is described. By this method, the Michael adducts are obtained in good to excellent yields in short reaction times under thermal and microwave conditions.

Catalytic amounts of heteropoly acids and polyoxometalates promoted mononitration of phenolic compounds using iron(III) nitrate nonahydrate and bismuth(III) nitrate pentahydrate in dichloromethane at room temperature. Tungstophosphoric acid cesium salt, Cs2.5H0.5PW12O40, in a heterogeneous phase, exhibited significant rate enhancement of reactions as well as ortho selectivity without over-nitration and oxidation byproducts.

A new series of unsaturated polycarbonyl compounds in which the keto group attached to olefinic linkage has been synthesized by the reaction of acetoacetanilide and aromatic aldehydes under specified conditions. The existence of these compounds predominantly in the intramolecularly hydrogen bonded enol form has been well demonstrated from their IR, 1H NMR and mass spectral data. Details on the formation of their complexes with Ni(II), Cu(II), and Zn(II) and their nature of bonding are discussed on the basis of analytical, IR, 1H NMR and mass spectral data.