Journal of the Iranian Chemical Society
Volume:8 Issue: 2, June 2011

Due to their versatility and diversity, catalytic multi-component isocyanide-based reactions (IMCR), are very interesting and important. Isocyano group is a unique functional group due to its reactivity toward electerophiles and nucleophiles at the same atom. It participates in many multi-component reactions along with various catalysts which dramatically improve reaction conditions for the achievement of better yields, milder and benign reaction condition and in some cases better stereoselectivities. In this review, we wish to disclose the recent applications of metal, basic, acidic and many other catalytic systems in the IMCRs. In supplementary section we also updated our review with all related publications in 2010.

A rapid and highly sensitive method is described for the extraction and determination of di- and tributyltin in PVC samples using headspace liquid phase microextraction followed by an analysis with graphite furnace atomic absorption spectrometry (HS-LPME/GFAAS). The analytes were derivatized in situ with sodium tetraethylborate and concentrated in a 2 µl microdrop of benzyl alcohol suspended from the tip of a conventional GC microsyringe. The ethylated species then were directly transferred into a graphite furnace and quantified. The extractions were carried out for 5 ml sample solution (8 ml vial) adjusted at pH 5, with derivatization at 22 °C for 15 min in a 2% sodium tetraethylborate. The experimental parameters impacting the performance of HS-LPME were also investigated. According to the analysis, the linearity range was from 5.0 to 250.0 ng l-1 with a detection limit of 0.5 ng l-1 for dibutyltin and from 1.7 to 170.0 ng l-1 with a detection limit of 0.17 ng l-1 for tributyltin. Method RSD values were below 1.5%. Finally, the analysis of spiked PVC and water samples revealed that matrix had little effect upon extraction.

A chemoselective and efficient procedure for the oxidation of alcohols to the corresponding carbonyl compounds is reported using ceric ammonium nitrate in the presence of 3-methylimidazolium hydrogensulfate as Brönsted acidic ionic liquid ([Hmim]HSO4) as the solvent under mild conditions. The use of non-toxic and inexpensive materials, straightforward procedure, short reaction times and good yields of the products are the major advantages of this method.

Two new manganese complexes of {Mn[(2-py)CNOH]2Cl2} (1) and {Mn[(2-py)CNOH]2(OAc)2} (2) were synthesized and their structures were characterized by X-ray crystallography, IR spectroscopy and elemental analysis. Two complexes were used as bulk modifier to fabricate two carbon paste electrodes (Mn-CPE: 1-CPE and 2-CPE). The electrochemical behaviors of two modified electrodes were characterized by cyclic voltammetry. They have similar electrochemical behaviors and good electrocatalytic activities toward the reduction of hydrogen peroxide and nitrite. The results are reproducible with a lower detection limit than earlier reports. There exist a good linear relationship between peak current with the concentration in the range of 0.10-1.20 μM and a detection limit of 0.08 μM for hydrogen peroxide, and in the range of 0.02-0.10 μM and a detection limit of 0.01 μM for nitrite. Also Mn-CPE exhibits remarkable long term stability, simple preparation and inexpensive material, which is important for practical application on electrochemistry sensors.

A novel Mitsunobu-based protocol has been developed for the synthesis of carbazates and dithiocarbazates through the variety of corresponding primary, secondary and tertiary alcohols and various kinds of substituted hydrazines using Mitsunobu’s reagent and CO2/CS2 system, in good to excellent yields.

An efficient and environmentally friendly procedure has been developed for the synthesis of symmetrical and unsymmetrical acyclic imides by the reaction of nitriles with acyclic anhydrides in the presence of catalytic amounts of 12-tungstophosphoric acid (H3PW12O40) under thermal conditions and microwave irradiation. It was found that microwave improves the yields and significantly reduces the reaction times. Furthermore, the catalyst could be recovered and reused several times without decrease in its activity.

In this work, a green, simple and highly efficient procedure for the synthesis of bis(indolyl)methanes and 4,4′×-(arylmethylene)-bis(3-methyl-1-phenyl-1H-pyrazol-5-ol)s [as an important class of bis(pyrazolyl)methanes] is described. The condensation of indoles or 1-phenyl-3-methylpyrazol-5-one with carbonyl compounds catalyzed by poly(ethylene glycol)-bound sulfonic acid (PEG-SO3H) in water affords the title compounds in high yields and relatively short reaction times.

DFT studies on the proposed mechanisms of the initial stage of Maillard reaction between α-fructose (α-Fru)/β-fructose (β-Fru)/open chain fructose (O-Fru) and glycine (Gly) under different conditions revealed that α-Fru was more reactive than β-Fru and O-Fru, and O-Fru was less reactive than β-Fru in the reaction. The reaction under basic conditions was found to be the most favorable for the formation of the Heyns rearrangement products (HRPs) in the initial stage, and the aqueous solution was found to be more feasible than the gaseous state reaction. The reaction under neutral conditions was the second most favorable for the production of HRPs. The reaction at the isoelectric point of glycine and under acidic conditions was found to be unfeasible to produce HRPs.

Simultaneous kinetic-potentiometric determination of binary mixture of permanganate (MnO4-) and dichromate (Cr2O72-) by H-point standard addition method (HPSAM), partial least squares (PLS) and principal component regression (PCR) is described. In this work, the difference between the rate of the oxidation reaction of Fe(II) to Fe(III) in the presence of MnO4- and Cr2O72-formed the basis of the method. The rate of the consumed fluoride ion for making the complex was detected by a fluoride ion selective electrode (FISE). The results show that the simultaneous determination of MnO4- and Cr2O72-could be conducted in their concentration ranges of 0.5-10.0 and 0.1-20.0 µg ml-1, respectively. The total relative standard error (RSE) for applying the PLS and PCR methods to 9 synthetic samples was 5.30 and 3.17, respectively in the concentration range of MnO4-, and 3.30 and 2.04, respectively, in the concentration range of Cr2O72-. In order for the selectivity of the method to be assessed, we evaluated the effects of certain foreign ions upon the reaction rate. The proposed methods (HPSAM, PLS and PCR) were evaluated using a set of synthetic sample mixtures and then applied to the simultaneous determination of MnO4- and Cr2O72-in different water samples.

A one-pot, three-component coupling reaction of aldehydes, amines and alkyne (A3-coupling) via C-H activation using perflorinated resinsulphonic acid (Nafion®NR50) as a recyclable and environmentally benign catalyst for the synthesis of propargylamine derivatives is described. This protocol avoids the use of heavy metals, co-catalysts and produces the propargylamines in excellent yields.

The oxidative decarboxylation of various α-aryl- and α,α-arylcarboxylic acids having electron-donating and electron-withdrawing groups by using a stoichiometric amount of potassium 12-tungstocobaltate(III), K5CoIIIW12O40, in 50% aqueous acetonitrile solution resulted in the corresponding aldehydes and ketones in high yields within short reaction times under microwave irradiation. This transformation was also carried out under the conventional heating conditions which produced the corresponding aldehydes and ketones in relatively longer reaction times. The arylacetic acids with electron-withdrawing substituents required longer reaction times and produced lower yields. In contrast to arylacetic esters which were inert toward decarboxylation, the sodium arylacetates were decarboxylated in shorter times with yields better than those of the parent acids.

Three new Schiff base adducts, [SnMe2Cl2(H2cdnaphen)] (1), [SnPh2Cl2(H2cdnaphen)2].C6H6 (2) and [SnBu2Cl2(H2cdnaphen)2] (3) were synthesized by the reaction of SnR2Cl2 (R = Me, Bu and Ph) with a Schiff base ligand, Methyl 2-[2-(2-hydroxynaphthaldimino)ethylamino]-1-cyclopentene-1-dithiocarboxylate (H2cdnaphen). The new products were characterized by elemental analysis, IR, 1H NMR and 119Sn NMR spectroscopies. Spectroscopic data suggest that H2cdnaphen exists predominately in keto-amine tautomeric form and in all complexes acts as a monodentate neutral ligand coordinating with the metal through oxygen atom, while the sulfur atom and imine nitrogen are not involved in coordination with the tin. Thermal decomposition of the complexes was studied through thermogravimetry and the thermodynamic activation parameters were determined by the Coats-Redfern method.

Reaction of 18-crown-6 with KI in ethanol solution followed by addition of iodine (I2) afforded a unique triiodide salt with a nanotube-like structure ({[K.18-Crown-6]I3}n). It is shown that this reagent may be used for the chemoselective trimethylsilylation of alcohols. The synthesis of the crystalline reagent is a good example of crystal engineering. Reagent was recycled and reused.

A new ionic liquid 1-(3-trimethoxysilylpropyl)-3-methylimidazolium nitrite was synthesized. This ionic liquid was used as a convenient nitrosonium source in diazotization of arylamines into their corresponding diazonium salts which were converted into their related azo dyes via the in situ azo-coupling with aniline derivatives or phenolic compounds. The diazotization of anilines in this ionic liquid and subsequent azo-coupling generated the related azo dyes in good to excellent yields at 0-5 °C in short reaction times via a simple experimental procedure.

The spectral behavior of some benzaldehyde hydrazones was examined via the UV spectroscopic technique at room temperature and in the pH region between 1 and 7 in aqueous perchloric acid medium. The acid-base equilibrium was characterized qualitatively and quantitatively. It was found that the protonation reaction took place. The spectra of the solution of benzaldehyde hydrazones at different pHs were studied and utilized for the determination of ionization constants of the protonated forms of hydrazones (pKBH+). The pKBH+ values were determined numerically and graphically from the absorbance values of the experimental and reconstructed spectra by characteristic vector analysis. In order to obtain thermodynamic pKBH+ values, measurements were performed at ionic strengths of 0.1, 0.25 and 0.5 M (NaClO4). There was a good agreement between the obtained pKBH+ values of the investigated hydrazones and those of similar classes of compounds. The site of protonation of the investigated hydrazones was also studied, too. The proton affinities for the different nitrogen atoms of the hydrazone molecule were calculated using AM1 and PM3 semiempirical methods. It was demonstrated that the protonation occurred at the imino nitrogen atom of hydrazone molecule. The effect of the chemical structure on the ionization constants was also examined.

12-Tungstophosphoric acid immobilized on [bmim][FeCl4] was found to be an efficient catalyst for chemoselective methoxymethylation and ethxoymethylation of alcohols and also one-pot conversion of MOM- or EOM-ethers to their corresponding acetates and TMS-ethers under thermal conditions and microwave irradiation. These procedures were simple, rapid and the corresponding products were obtained in high yields. The catalyst exhibited remarkable reactivity and was reusable.

A facile and one-pot protocol for the synthesis of 2-alkylthio-1,3,4-oxadiazoles is reported. This green method relies on the reaction of acid hydrazides with CS2 and an alkyl halide. The reaction is carried out under mild and environmentally friendly procedure in water with high to excellent yields. Thirteen different valuable alkylthio-1,3,4-oxadiazoles are synthesized from cheap and easily available CS2 with this method. This is the first report for the synthesis of 1,3,4-oxadiazoles in water.

An environmentally benign and efficient process for the preparation of monobromo derivatives of aryl aldehydes and ketones was developed by simple and practical reactions of aryl aldehydes or ketones with 1,3-di-n-butylimidazolium tribromide ([BBIm]Br3), as a brominating reagent under solvent-free conditions in very high yields. The process has several advantages: high conversions, short reaction time, mild reaction conditions, simple workup with good to quantitative yields and re-usable ionic liquid.

Tetrabutylammonium phthalimide-N-oxyl (TBAPINO) was found to be an effective organocatalyst for rapid, simple and chemoselective protection of the hydroxyl group of alcohols and phenols using hexamethyldisilazane (HMDS) under mild conditions. The low catalyst loading, high to quantitative yields and simple removal of the catalyst from the reaction mixture illustrate the other attractive features of this protocol.

A new ionic liquid, 3-hydroxypropanaminium acetate (HPAA) [H3N+-CH2-CH2-CH2-OH][CH3COO-], was synthesized for the first time and used as an efficient and recoverable catalyst in the synthesis of 2-amino-5-oxo-4,5-dihydropyrano[3,2-c]chromene-3-carbonitrile derivatives by condensing together 4-hydroxycoumarin, aldehydes and malononitrile at room temperature. The catalyst can be reused for four times without noticeable loss of activity.

Protein aggregation and denaturation are two major limitations in bioprocess engineering and protein processing. In the present study, we investigated the effects of β-cyclodextrin, as an artificial chaperone, on the structure and function of lysozyme using UV-Vis, fluorescence spectrophotometry, isothermal titration calorimetry (ITC) and theoretical approaches of docking. Lysozyme was entirely aggregated in a solution containing 0.1% lysozyme (w/v), 150 mM sodium phosphate buffer (pH 7.2), and 10 mM dithiotreitol (DTT). The absorption changes were monitored at 37 �°C for 50 min using a UV-Vis spectrophotometer at 360 nm. The residual lysozyme activity was determined using chitosan, a polysaccharide, whose structure is similar to a bacterial cell wall, as a substrate. The effect of β-cyclodextrin on lysozyme activity was determined in the presence and absence of DTT. Our findings indicated that β-cyclodextrin increased the enzyme activity and its kinetics stabilization by binding to Trps 62 and 63, which are embedded in the core of the enzyme inducing its disaggregation. These occurred through the disruption of hydrophobic interactions as demonstrated by ANS fluorescence spectrophotometry. Furthermore, ITC analysis indicated that the binding of β-cyclodextrin to lysozyme was an endothermic reaction and reduced thermodynamic stability by partial unfolding of the enzyme. Thus, the interaction of β-cyclodextrin with lysozyme reduces themodynamic stability by inducing partial unfolding of the enzyme.

Perovskite calcium titanate (CaTiO3) nanowires with average diameters in the range of 120-130 nm were grown by hydrothermal treatment of commercial anatase-titania (TiO2) and calcium chloride in aqueous sodium hydroxide solution (2.5-13 M). Reactions were carried out in temperature range of 110-150 �°C at various pH (9-13) for 12-72 h. The study revealed that these parameters affect the crystal morphology and size of crystallites. Reaction products obtained at different stages were characterized by thermogravimetry (TG) and differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The XRD analysis revealed the formation of CaTiO3 phases with orthorhombic crystal structure. Thermal analysis results showed that anatase-TiO2 was thermally stable below 400 �°C and at higher temperatures anatase transforms to rutile phase whereas CaTiO3 was stable up to 850 �°C.

Reductive cleavage of benzylic acetal, ketal and ether compounds to the corresponding alkanes using triethylsilane and a catalytic amount of palladium(II) chloride is described. The reductive reaction took place under mild conditions, affording high yields of the corresponding alkane compounds in short reaction times.

In this study, using a one-dimensional phospholipids model, we have introduced an exact combinatorial factor method for the investigation of order-disorder in the phospholipids lattice. Our assumption was that the lattice was composed of six groups, and for simplicity, we assumed that the total energy of the lattice can be considered as the rotational energy of gauche molecules and the nearest neighbor interactions between trans molecules. Using the combinatorial factor method (CFM), the total energy and the corresponding constrains, the Helmholtz free energy was minimized. Finally, the thermodynamic properties of the one-dimensional lattice including the internal energy, entropy, and heat capacity were determined, exactly. The results show that, adopting such a model and under specific conditions, a phase transition, similar to the one in Onsager transition, takes place.