• Volume 126, Issue 6

November 2014,   pages  1623-1988

• Synthesis and properties of a dual responsive hydrogel by inverse microemulsion polymerization

A novel dual responsive hydrogelwas synthesized by inversemicroemulsion polymerization, using itaconic acid as pH-responsive monomer and N- isopropylacrylamide as thermo-responsivemonomer. pH- and temperature-sensitivity and dynamic viscoelasticity behaviour of the dual responsive hydrogels were investigated. Dual responsive hydrogels showed remarkable pH- and temperature-sensitivity and enhanced viscoelastic behaviour under high stress. Temperature-induced shrinkage range of the dual responsive hydrogels was higher and broader than that of the conventional poly(N-isopropylacrylamide) hydrogel. FTIR revealed the structure of dual responsive hydrogels. The as-synthesized regular and sphere-like hydrogel particles had the average particle size of 49 nm in the range of 30-78 nm.

• Investigation of Keto-enol Tautomers during the Synthesis of Aryl-bis (2-hydroxy-1-naphthyl)Methanes

This study investigated the existence of keto-enol tautomers for the first time during the synthesis of aryl-bis(2-hydroxy-1-naphthyl)methane from 2-naphthol and 𝑝-tolualdehyde or 4-chlorobenzaldehyde in methanol using CuSO4.5H2O as catalyst under reflux condition. The exclusive formation of aryl-bis(2-hydroxy-1-naphthyl)methaneswas observed in dichloromethane at room temperature in the presence of BF3.OEt2/AcOH as catalyst. The keto productswere isolated and characterized by 1HNMR, 13C NMR, COSY and DEPTspectra.

• Synthesis, crystal structure and catecholase activity of a Ni(II) complex derived from a tetradentate Schiff base ligand

A new nickel(II) complex [Ni(L)] (1) [H2L = 1,1′-(1E,1′E)-(propane-1,3-diylbis(azan-1-yl-1-ylidene))bis(methan-1-yl-1-ylidene)dinaphthalen-2-ol] was synthesized and X-ray crystallographically characterized. 1 crystallizes in orthorhombic crystal system with Cmc21 space group. The unit cell dimensions of the crystal are a = 30.6345(4)Å, b = 8.45340(10)Å, c = 7.75180(10)Å. Structural analysis reveals a tetradentate chelation behaviour of the dianionic ligand H2L having a distorted square planar geometry around Ni(II) with NiN2O2 chromophore in 1. The title complex 1 behaves as an effective catalyst towards oxidation of 3,5-ditertiarybutyl catechol (3,5-DTBC) in acetonitrile to its corresponding quinone derivative in air. The reaction follows first-order reaction kinetics with rate constant 4.28 × 10−5 min-1. The reaction follows Michaelis-Menten enzymatic kinetics with a turnover number of ($K_{cat}$) 140.72 h-1 in acetonitrile.

• Polyoxometalate coordinated transition metal complexes as catalysts: Oxidation of styrene to benzaldehyde/benzoic acid

Oxidation of styrene is carried out by using heptamolybdate coordinated transition metal (Co2+, Zn2+) complexes, [2-ampH]4[{Co(H2O)5}Mo7O24]·9H2O (1), [3-ampH]4[{Co(H2O)5}Mo7O24]·9H2O (2), [2-ampH]4[{Zn(H2O)5}Mo7O24]·4H2O (3) and [3-ampH]4[{Zn(3-ampy)(H2O)4}Mo7O24]·4H2O (4) as catalysts and H2O2 as an oxidant at 80°C. The leaching study has been carried out to check the quality of catalyst and it has been reused for three times with good percentage of conversion. For the first two catalysts (compounds 1 and 2), the major product obtained is benzaldehyde, and benzoic acid is the major product for next two catalysts (compounds 3 and 4). Stability of the catalysts has been analyzed by IR, UV-spectroscopy and powder X-ray crystallography.

• Two new twisted helical nickel(II) and cobalt(III) octahedral monomer complexes: Synthesis and structural characterization

Two mononuclear complexes namely [NiII(L)] (1) and [CoIII(L)](NO3) (2) of a hexacoordinating N4O2 donor Schiff base ligand were synthesized and characterized by single crystal X-ray studies. In compound 2 the central cobalt is in +3 oxidation state while `in' compound 2, the nickel ion is in +2 oxidation state. The two complexes are isostructural with octahedral coordination environment exhibiting helical twist topology. They also display strong H-bonding as well as CH-𝜋 interactions to generate 1D chain.

• Mechanistic chemistry of oxidation of balsalazide with acidic chloramine-T and bromamine-T: A comparative spectrophotometric kinetic study

Balsalazide (BSZ) belongs to a class of non-steroidal anti-inflammatory drugs. Kinetics and mechanism of oxidation of BSZ with sodium N-halo-p-toluenesulfonamides viz., chloramine-T(CAT) and bromamine-T(BAT) in HClO4 medium have been spectrophotometrically investigated ($\lambda_{\max}$ =357nm) at 303 K. Under comparable experimental conditions, reactions with both the oxidants follow a first-order dependence of rate on [BSZ] and fractional-order dependence on each [oxidant] and [HClO4]. Activation parameters and reaction constants have been computed. 2-hydroxy-5-nitroso-benzoic acid and 3-(4-nitroso-benzoylamino)-propionic acid are identified as the oxidation products of BSZ with both CAT and BAT. The rate of oxidation of BSZ is about five-fold faster with BAT than with CAT. Plausible mechanism and related rate law have been deduced for the observed kinetics.

• Cyanide- and phenoxo-bridged heterobimetallic Fe(III)-Mn(III) complexes: Synthesis, crystal structures and magnetic properties

By employing two $mer$-tricyanidoiron(III) precursors [Ph4P][FeIII(pcq)(CN)3] and [Ph4P][FeIII (pzq)(CN)3] as building blocks and a salen-tpye Schiff-basemanganese (III) compound as assembling segment, two tetranuclear cyanide- and phenoxo- bridged heterobimetallic Fe(III)-Mn(III) complexes {[Mn(saltmen)] [Fe(pcq)(CN)3]}2·2CH3OH (1) and {[Mn(saltmen)] [Fe(pzq)(CN)3]}2·2CH3OH (2) (pcq = 8-(pyridine-2-carboxamido, pzq = 8-(pyrazine-2-carboxamido, saltmen2− = N,N′-(1,1,2,2-tetramethylethylene)bis(salicylideneaminato) dianion) have been synthesized and characterized by elemental analysis, IR spectroscopy and X-ray structure determination. Single x-ray analysis reveals their isostructural cyanide-bridged Fe(III)-Mn(III) binuclear structure. The binuclear entity is self-complementary through phenoxo oxygen from the neighbouring complex, giving cyanide- and phenoxo- bridged tetranuclear structure. Furthermore, under the help of the intermolecular 𝜋-𝜋 interaction, these two complexes can be constructed into 1D infinite chain supramolecular structure. Investigation over magnetic susceptibilities reveals the overall ferromagnetic coupling between the adjacent Fe(III) and Mn(III) ions bridged by cyanide group with 𝐽 = 5.34 cm-1 and 5.55 cm-1 for complexes 1 and 2, respectively.

• Synthesis, structural investigation and kinetic studies of uranyl(VI) unsymmetrical Schiff base complexes

Uranyl(VI) complexes with unsymmetrical N2O2 Schiff base ligands were synthesized and characterized. Their characterization was performed using UV-Vis, 1H NMR, cyclic voltammetry, single-crystal X-ray crystallography, IR, TG and C.H.N. techniques. X-ray crystallography of the complexes show that beside coordination of the tetradentate Schiff base, one DMF molecule is also coordinated. In order to investigate the effect of the substitutional groups of the Schiff base on the oxidation and reduction potentials, we used the cyclic voltammetry method. Electrochemistry of these complexes showed that the presence of electron releasing groups accelerates oxidation of the complexes. The kinetics of thermal decomposition was studied using thermal gravimetric method (TG) and Coats-Redfern equation. According to Coats-Redfern plots, the kinetics of thermal decomposition of the studied complexes is first-order in all stages. Also the kinetics and mechanism of the exchange reaction of the coordinated solvent with tributylphosphine was carried out in solution, using spectrophotometric method. As a result, the second order rate constants at four temperatures and the activation parameters were calculated showing an associative mechanism for all corresponding complexes. It was concluded that the steric and the electronic properties of the complexes influence the reaction rate significantly.

• An anti-ferromagnetic terephthalate-bridged trigonal prismatic dinuclear manganese(II) complex: Synthon of rare anion$^{\ldots} \pi$ interaction promoting dimensionality

A dinuclear compound [Mn2(L)2(𝜇-tp)](PF6)2·3.57H2O (1) [L = N,N′-(bis(pyridin-2-yl)benzylidene)-1,3-propanediamine and tp = terephthalate dianion] has been isolated and characterized on the basis of microanalytical, spectroscopic and other physicochemical properties. X-ray structural study showed interesting bis(bidentate) bridging motif of tp in the dicationic dinuclear unit [Mn2(𝜇-tp)]2+. Each manganese(II) centre adopts a rare distorted trigonal prismatic geometry with an MnN4O2 chromophore.Chelation of the tetradentate Schiff base (L) along with bis(bidentate) bridging of two O atoms of tp complete hexacoordination around each manganese(II) centre. The dinuclear units of 1 are associated through cooperative C-H$\cdots$F hydrogen bonds and $\pi^{\cdot} \pi$, C-H$^{\cdots} \pi$ and rare anion$^{\cdots} \pi$ interactions to promote the dimensionality in a graded manner. Variable temperature magnetic susceptibility measurement of 1 in the 2-300 K temperature range revealed weak antiferromagnetic interaction presumably due to long bridging arm of tp.

• Polymer supported nickel complex: Synthesis, structure and catalytic application

In the present investigation, a new synthetic route for a novel recyclable free [3-MOBdMBn-Ni] and polystyrene-anchored [P-3-MOBdMBn-Ni] nickel complexes is presented. The free and polymer-anchored metal complexes were synthesized by the reaction of nickel (II) with one molar equivalent of unsupported N N′-bis (2-Hydroxy-3-methoxybenzaldehyde) 4-Methylbenzene-1,2-diamine (3-MOBdMBn) or polymersupported (P-3-MOBdMBn) Schiff-base ligand in methanol under nitrogen atmosphere. The advantages of these polymer-supported catalysts are the low cost of catalyst and recyclability up to six times, due to easy availability of materials and simple synthetic route. The higher efficiency of complexation of nickel on the polymer-anchored 3-MOBdMBn Schiff base than the unsupported analogue is another advantage of this catalyst system. The structural study reveals that nickel(II) complex of 3-MOBdMBn is square planar in geometry. The catalytic activity of nickel complex towards the oxidation of phenol was investigated in the presence of hydrogen peroxide. Experimental results indicate that the reactivity of P-3-MOBdMBn-Ni was dramatically affected by the polymer support compared to free 3-MOBdMBn-Ni. The rates of oxidation (R$_p$) for unsupported and supported catalysts are 1.37 × 10-6 mole dm-3 s-1 and 2.33 × 10-6 mole dm-3 s-1 respectively.

• A cross-linked manganese porphyrin as highly efficient heterogeneous catalyst for selective oxidation of cycloalkenes/alkanes

The monomeric tetrakis (5,10,15,20-𝑝-bromophenyl) manganese porphyrin has been converted to a micro- and mesoporous material of surface area 1301m2/g by carefully manipulating the reaction conditions of Suzuki coupling. This material has been tested for its oxidizing ability of cycloalkenes/alkane by 𝑡-BuOOH, H2O2, CumOOH and m-CPBA. The catalyst is found to oxidize the alkenes selectively and it is not destroyed even 5% in 10 cycles of successive oxidation processes in one pot. The parent monomer gets destroyed appreciably under similar oxidizing conditions.

• Nano copper and cobalt ferrites as heterogeneous catalysts for the one-pot synthesis of 2,4,5-tri substituted imidazoles

A simple one-pot synthesis has been developed for the synthesis of 2,4,5-trisubstituted imidazoles using magnetic recyclable spinel nano copper and cobalt ferrites by the condensation of benzil, aromatic aldehyde and ammonium acetate in ethanol as solvent. The reaction, with these catalysts was carried out under mild reaction conditions with very good yields of substituted imidazoles. These catalysts can be recycled very easily and reused, which makes this methodology environmentally benign.

• Functionalization of lambda-zirconium phosphate with ethylenediaminetetraacetic acid: Synthesis, characterization and applications

A new layered organic-inorganicmaterial based on 𝜆-Zirconium phosphate (𝜆-ZrP) and ethylenediaminetetraacetic acid (H4Y) has been prepared. The thermal analyses, X-ray diffractometry and FT-IR spectrophotometry confirm the introduction of H4Y inside the interlayer gallery of 𝜆-ZrP. The pristine 𝜆-ZrP and its new polyaminocarboxylic acid functionalized derivative (𝜆-ZrPH2Y) exhibit high potential for the application in the area of hard water treatment, where their Ca2+ uptake capacities are found to be 32.0 and 40.4mg Ca2+ per gram of 𝜆-solid, respectively.

• Sulfonated graphenes catalyzed synthesis of expanded porphyrins and their supramolecular interactions with pristine graphene

A newer synthesis of sulfonic acid functionalized graphenes have been developed, which have been characterized, examined as heterogeneous solid acid carbocatalyst in the synthesis of selected expanded porphyrins in different reaction conditions. This environment-friendly catalyst avoids the use of toxic catalysts and enhances the yields of porphyrinoids. The non-covalent interaction of porphyrinoids has also been studied with exfoliated graphene solution in organic solvents by UV-Visible and fluorescence spectroscopy.

• Understanding the structure and electronic properties of N-doped graphene nanoribbons upon hydrogen saturation

Structures and electronic properties of zigzag graphene nanoribbon (ZGNR) with pyridine (3NVZGNR) functionalized by Scandium (Sc) at the edge were studied through quantum chemical calculations in the formalism of density-functional theory (DFT). Pyridine-like nitrogen defects is very crucial for enhancing the Sc atom binding to the defects and is thermodynamically favoured. During Sc decoration of ZGNR there is a shift from 0.35 eV small gap semiconductor regime to that of a metal which can be used for band gap tuning by controlled saturation of Sc. ZGNR decorated with Sc can attract H2. Upon saturation of multiple H2 in quasi-molecular fashion, the metallic character is converted to semiconductors of small gap of 0.10 eV, which are predicted to be interesting materials not only for hydrogen storage but also for their band gap engineered properties.

• Sequential bond energies and structures of the Cr+·(N2)$_n$, n =1−4

DFT calculations, with an effective core potential for the chromium ion and large polarized basis set functions have been used to calculate the sequential bond dissociation energies of the Cr+·(N2)$_n$ (n = 1—4) complexes. A linear configuration was obtained for the Cr+·N2 and Cr+·(N2)2 complexes with sequential bond dissociation energies of 14.6 and 16.4 kcal mol-1, respectively. For the Cr+·(N2)3 and Cr+·(N2)4 complexes, distorted trigonal pyramidal and tetrahedral geometries were optimized with sequential bond dissociation energies of 6.5 and 5.5 kcal mol-1, respectively. 𝜋- back-donation in side-on approach of the Cr+·N2 leads to the formation of a tilted structure with the Cr+ ion in central position. The di-ligated complex exhibits the strongest bond dissociation energy among these four Cr+·(N2)$_n$ (n = 1—4) complexes since it has the largest Cr+—N bond order.

• Computational studies on energetic properties of nitrogen-rich energetic materials with ditetrazoles

Based on the full optimized molecular geometric structures at B3LYP/6-311++G$^{\ast\ast}level, the densities (𝜌), heats of formation (HOFs), detonation velocities (D) and pressures (P) for a series of ditetrazoles derivatives, were investigated to look for high energy density materials (HEDMs). The results show that the influence of different substituted groups on HOFs has the order of -N3&gt;-CN&gt;-NH2&gt;-NO2&gt;-NF2&gt;-ONO2&gt;-H&gt;-CH3&gt;-CF3. The introduction of -CF3 groups is more favourable for increasing the density and the introduction of -CH3 groups is not favourable for increasing the density. In addition, all the series combined with -NF2 group except B-NF2 all have higher densities, larger D and P. F-NF2 may be regarded as the potential candidates of HEDMs because of the largest detonation velocity and pressure among these derivatives.The energy gaps between the HOMO and LUMO of the studied compounds are also investigated. • Theoretical study on O$\cdots$Br and O$\cdots$Cl halogen bonds in some small model molecular systems Halogen bonding interactions of type X$\cdots$O=C are important in various fields including biological systems. In this work, theoretical calculations were carried out using B3LYP/6-31++G∗∗, MP2/6-31++G∗∗ and MP2/aug-cc-pVDZ methods on a series of O$\cdots$X halogen bonds between CH2O andCH3CHO as halogen bond acceptor with X-Y (X = Cl, Br; Y = CF3, CF2 H, CFH2, CN, CCH, CCCN) as halogen bond donors. The strength of interaction energy for O$\cdots$Br halogen-bonded complexes varies from −2.16 to −5.26 kcal/mol while for O$\cdots$Cl complexes, it is between −1.65 to −3.67 kcal/mol, which indicate the O$\cdots$Br bond to be stronger in comparison to O$\cdots$Cl bond. SAPT analysis suggests that the strength of halogen bonding arises from the electrostatic and induction forces while dispersion is playing a comparatively smaller role. The halogen-bonded interaction energies were found to correlate well with positive electrostatic potential V$_{\text{S,max}}$, halogen bonded distances, and the change in s-character of C-X bond. The halogen-bonded interaction energies were also evaluated for O$\cdots$I bonded complexes and thus these complexes were found to be stronger than O$\cdots$Br and O$\cdots$Cl bonded complexes. • Structure, bonding and energetics of N-heterocyclic carbene (NHC) stabilized low oxidation state group 2 (Be, Mg, Ca, Sr and Ba) metal complexes: A theoretical study A series of N-heterocyclic carbene stabilized low oxidation state group 2 metal halide and hydrides with metal-metal bonds ([L(X) M-M(X) L]; L = NHC ((CHNH)2C:), M = Be, Mg, Ca, Sr and Ba, and X = Cl or H) has been studied by computational methods. The main objective of this study is to predict whether it is possible to stabilize neutral ligated low oxidation state alkaline-earth metal complexes with metal-metal bonds. The homolytic metal-metal Bond Dissociation Energy (BDE) calculation, Natural Bond Orbital (NBO) and Energy Decomposition Analyses (EDA) on density functional theory (DFT) optimized [L(X)M-M(X)L] complexes revealed that they are as stable as their 𝛽-diketiminate, guanidinate and 𝛼-diimine counterparts. The optimized structures of the complexes are in trans-linear geometries. The bond order analyses such as Wiberg Bond Indices (WBI) and Fuzzi Bond Order (FBO) confirm the existence of single bond between two metal atoms, and it is covalent in nature. • A computational study on kinetics, mechanism and thermochemistry of gas-phase reactions of 3-hydroxy-2-butanone with OH radicals Theoretical investigation has been carried out on the kinetics and reaction mechanism of the gas-phase reaction of 3-hydroxy-2-butanone (3H2B) with OH radical using dual-level procedure employing the optimization at DFT(BHandHLYP)/6-311++G(d,p) followed by a single-point energy calculation at the CCSD(T)/6-311++G(d,p) level of theory. The pre- and post reactive complexes are also validated at entrance and exit channels, respectively. Thus reaction may be proceed via indirect mechanism. The intrinsic reaction coordinate (IRC) calculation has also been performed to confirm the smooth transition from a reactant to product through the respective transition states. The rate coefficients were calculated for the first time over a wide range of temperature (250-450 K) and described by the following expression: kOH = 7.56 × 10−11exp[−(549.3 ± 11.2)/T] cm3 molecule-1s-1. At 298 K, our calculated rate coefficient 1.20 × 10−11 cm3 molecule-1 s-1 is in good agreementwith the experimental results. Our calculation indicates that H-abstraction from 𝛼-C-H site of 3H2B is the dominant reaction channel. Using group-balanced isodesmic reactions, the standard enthalpies of formation for 3H2B and radicals generated by hydrogen abstraction are reported for the first time. The branching ratios of the different reaction channels are also determined. Also, the atmospheric lifetime of 3H2B is also calculated to be 1.04 days. • Theoretical study on the detailed repair of O6-methyl guanine to guanine by cysteine The repair process of O6-methylguanine (O6mG) by cysteine (Cys145) has been studied using the quantum mechanical calculations in the presence of solvent water molecules and also using the polarizable continuum model (PCM). The proton transfer from Cys145 to O6mG, directly and mediated by bridged water molecules, has been considered to investigate the role and the sequence of the proton transfer on the repair process. In both models, the energy barrier of the methyl transfer is reduced when the proton is initially transferred from O6mG to Cys145. In addition, the protonation of N3 and N7 sites of O6mG in the acidic environment facilitates the repair process. Results of this study help to understand repair mechanisms of damaged DNA bases better on the basis of proton transfer between that and nucleic acids. • Hydrogen bonding of formamide, urea, urea monoxide and their thio-analogs with water and homodimers Ab initio and DFT methods have been employed to study the hydrogen bonding ability of formamide, urea, urea monoxide, thioformamide, thiourea and thiourea monoxide with one water molecule and the homodimers of the selected molecules. The stabilization energies associated with themonohydrated adducts and homodimers’ formation were evaluated at B3LYP/6-311++G^{\ast\ast}$ and MP2/6-311++G∗∗ levels. The energies were corrected for zero-point vibrational energies and basis set superposition error using counterpoise method. Atoms in molecules study has been carried out in order to characterize the hydrogen bonds through the changes in electron density and laplacian of electron density. A natural energy decomposition and natural bond orbital analysis was performed to understand the nature of hydrogen bonding.

• Ultrasound promoted and SiO2/CCl3COOH mediated synthesis of 2-aryl-1-arylmethyl-1𝐻-benzimidazole derivatives in aqueous media: An eco-friendly approach

Ultrasonic irradiation is an efficient and innocuous technique of reagent activation for synthesizing organic compounds. First one-pot synthesis of 2-aryl-1-arylmethyl-1H- benzimidazole derivatives from o- phenylenediamine and an aromatic aldehyde in the presence of silica gel supported trichloroacetic acid (SiTCA) was carried out with excellent yields at 50°C by sonication. This method provided several advantages such as green solvent, inexpensive catalyst, simple experimental methodology, shorter reaction time and higher yield.

• (𝑆)-Garner aldehyde derived Baylis-Hillman adduct: A potential substrate for the synthesis of D-$lyxo$ phytosphinosine analogue

A short, facile and efficient synthesis of D-lyxo-phytosphingosine analogue has been achieved. The key steps involved are the Baylis-Hillman reaction of (S)-Garner aldehyde with methyl acrylate to obtain the corresponding adduct as the potential substrate, to which was added decylmagnesium bromide to obtain the E-trisubstituted alkene followed by OsO4/NMO mediated dihydroxylation gave the desired D-lyxophytosphingosine analogue intermediate diol which on acid hydrolysis resulted in the formation of the target molecule in good yield.

• Facile synthesis of new thermally stable and organosoluble polyamide-imides based on non-coplaner phosphorus and silicon containing amines

Two new kinds of diamines, 3-[bis-(3-aminophenyl)-phosphinoyl)-phenyl]-3-(triphenylphosphoranylidene)-pyrrolidene-2,5-dione, (DAP) with phosphorus moiety and bis-(5-amino-naphthalene-1-yl) dimethyl silane (DAS) with silicon moiety are synthesized. A series of novel aromatic polyamide-imides (PAIs) are prepared from three dicarboxylic acids and synthesized diamines. The phosphorus and silicon containing diamines and all polymers are characterized by FT-IR, NMR spectroscopic techniques and elemental analysis. The polymers obtained have good thermal stability and glass transition temperature (T$_g$) in the range of 254-315°C. All these novel polyamide-imides (PAIs) contain 10% weight loss at the temperature above 506°C and more than 59% residue at 600°C in nitrogen atmosphere. The resulting polymeric films exhibit high optical transparency and inherent viscosity in the range of 0.68 to 0.79 dL/g. These polymers are found to be soluble in aprotic polar solvents such as NMP, DMSO, DMF and DMAc.Wide angle X-ray diffraction revealed that these polymers are predominantly amorphous in nature.

• Synthesis of 2-(oxadiazolo, pyrimido, imidazolo, and benzimidazolo) substituted analogues of 1,4-benzodiazepin-5-carboxamides linked through a phenoxyl bridge

Exceedingly facile single-step expedient protocols based on the versatility and reactivity of corresponding intermediates amidine and imidate (8 and 9), derived from 5-carboxamido-1,4-benzodiazepin-5-(4'-methylpiperazinyl)-carboxamide have been developed to provide an easy installation of the oxadiazole, pyrimidine, imidazole and benzimidazole (9-14) based privileged templates at 2-position of 5-carboxamido-1,4-benzodiazepin-5-(4'-methylpiperazinyl)-carboxamide (4), through a phenoxyl spacer, by utilizing the synthetic strategy depicted in schemes 1 and 2.

• First total synthesis of a guanidine alkaloid Nitensidine D using immobilized ionic liquid, microwaves and formamidinesulfinic acid

An efficient first total synthesis of a naturally occurring guanidine alkaloid, Nitensidine D isolated from ethanol extract of Pterogyne nitens has been described. Geraniol has been used as the starting material. N-alkylation of phthalimide has been achieved using immobilized ionic liquid and formamidinesulfinic acid acts as the guanylating reagent.

• Asymmetric synthesis of a functionalized tricyclo[6.2.0.02,6]decane ring system present in kelsoene and poduran

Synthesis of a functionalized tricyclo[6.2.0.02,6]decane derivative in enantiomerically pure form, the core structure present in the natural products kelsoene and poduran, is described. The key steps involve a stereocontrolled copper (I)-catalyzed intramolecular [2+2] photocycloaddition of a 1, 6-diene prepared from D-mannitol to form a substituted bicyclo[3.2.0]heptane derivative and a ring closing olefin metathesis involving the vicinal substituents on the five-membered ring of the bicyclo[3.2.0]heptane derivative.

• Behaviour of 4-[4-methoxy-3-methylphenyl]-4-oxobutenoic acid towards nitrogen-containing nucleophiles

A series of novel amino acid derivatives has been synthesized by the reaction of 4-[4-methoxy-3-methylphenyl]-4-oxobutenoic acid with primary and secondary amines. The treatment of amino acids with hydrazine afforded pyridazine. Phenylhydrazone was obtained from the reaction of the acid with phenyl hydrazine in ethanol. On the other hand, the acid underwent heterocyclization upon the treatment with 2-aminopyridine, 𝑜-phenylenediamine, aryldithiocarbamates and thiourea derivatives to give the corresponding pyridopyrimidine, quinoxalone, 2-thioxo-1,3-thiazole and 4-hydroxy-1,3-thiazole, respectively. The thiazolopyridazine derivatives were obtained from the reaction of 4-hydroxy-1,3-thiazole with hydrazine and phenylhydrazine, respectively. The behaviour of the 4-hydroxy-1,3-thiazole toward acetic anhydride and bromine was also studied. The proposed structures of the products were based on microanalytical and spectroscopic data. Some of the synthesized compounds also exhibited anti-microbial activities.

• Synthesis of quinolino[2′,3′:8,7]cyclooct[𝑏]indole

A rapid and efficient synthetic route for the synthesis of 7,8,9,10-tetrahydroquinolino[2′,3′:8,7] cyclooct[𝑏]indole analogues has been developed by reaction of 1-oxo-1,2,3,4,5,6-hexahydrocyclooct[𝑏]indole with anthranilic acid and 3-amino pyrazine acid under POCl3 condition and the synthesis of 7,8,9,10-tetrahydroquinolino[2′,3′:8,7]cyclooct[𝑏]indole-6-carboxylic acid has been designed by reaction of 1-oxo-1,2,3,4,5,6-hexahydrocyclooct[𝑏]indole with isatin in the presence of NaOH via Pfitzinger reaction. These methods are more satisfactory in terms of the yield and simple one-pot operation. Structures of the products thus obtained were confirmed by spectral studies.

• Fe(HSO4)3: An efficient, heterogeneous and reusable catalyst for 𝐶-alkylation of 𝛽-dicarbonyl compounds

Fe(HSO4)3(FHS) was used as an efficient catalyst for the heterogeneous addition of a series of benzylic and allylic alcohols to various 𝛽-dicarbonyl compounds, which afforded moderate to excellent yields of 𝐶-alkylated products in 1,2-dichloroethane. In comparison with the previous methods, the present research surprisingly exhibited higher reaction yields without formation of any by-products which could be formed by self-condensation of alcohols. Moreover, the catalyst can be readily recovered and reused up to five times with almost maintained reactivity and yields.

• Antioxidant and DNA damage inhibition activities of 4-Aryl-N-(4-arylthiazol-2-yl)-5,6-dihydro-4H-1,3,4-oxadiazine-2-carboxamides

A series of 4-aryl-𝑁-(4-pheny-thiazol-2-yl)-5,6-dihydro-4𝐻-1,3,4-oxadiazine-2-carboxamides were synthesized by condensing 4-aryl-5,6-dihydro-4𝐻-1,3,4-oxadiazine-2-carboxylic acid with 2-amino-4-aryl-thiazole derivatives. The newly synthesized molecules were characterized by spectral analysis and subjected to antioxidant and DNA damage inhibition studies.

• Oxidative ring cleavage of 2,3-dihydrophthalazine-1,4-dione in aqueous and non-aqueous solutions: Electrochemical and kinetic studies

Electrochemical oxidation of 2,3-dihydrophthalazine-1,4-dione (DHP) has been investigated in aqueous and some amphiprotic and aprotic non-aqueous solvents by cyclic voltammetric and controlledpotential coulometric techniques. Our data shows that electrochemically generated phthalazine-1,4-dione (PTD) in water and amphiprotic non-aqueous solvents participates in an oxidative ring cleavage (ORC) reaction to form phthalic acid. The rate of this reaction is dependent. On autoprotolysis constant ($K_{\text{SH}}$) and basicity of the solvent. Therefore, in the aprotic non-aqueous solvents such as acetonitrile and DMSO, the rate of ORC is too slow to be observed on the time-scale of cyclic voltammetry.

• How does fatty acid influence anti-thyroid drugs binding and specificity toward protein human serum albumin? A blind docking simulation study

This study reports an AutoDock-based blind docking simulation investigation to characterize the binding interaction of a series of anti-thyroid drugs (2-mercapto-1-methylimidazole (MMI), 2-thiouracil (TU), 6-methyl-2-thiouracil (MTU), 6-𝑛-propyl-2-thiouracil (PTU) with a model plasma protein Human SerumAlbumin (HSA) in the presence and absence of fatty acid (FA). The drug-protein binding efficiency is characterized in terms of binding free energy and the association constant (Ka, which is estimated as the reciprocal of the inhibition constant, Ki) of the drugs to the transport protein. The study also unveils the substantial impact of the presence of fatty acid (FA) on the binding interaction process. It is shown that in the presence of FA the drug-protein binding efficiency is markedly enhanced (except for MTU) and the binding location is changed. Hydrogen bonding interaction appears to play a governing role in the process of FA-induced modifications of binding efficiency and location.

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• # Journal of Chemical Sciences

Volume 132, 2020
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• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019