Multicomponent reactions involving tricyclooxonium ylide intermediate: diastereoselective synthesis of mono- and bisalkoxyoctahydro-1,4-benzodioxocin-6(5H)-one frameworks

A highly diastereoselective tandem ring-enlargement and aldol condensation process involving multicomponent reactions of ethereal tricyclooxonium ylide intermediate with alcohols, mono- or dialdehydes in the presence of titanium(iv) isopropoxide is described to furnish alkoxyoctahydro-1,4-benzodioxocin-6(5H)-one ring systems.     

Efficient atom economical one-pot multicomponent synthesis of densely functionalized 4H-chromene derivatives

A sequential one-pot, atom economical three component reaction yielding medicinally promising ethyl 2-amino-3-cyano-4-(2-ethoxy-2-oxoethyl)-5-oxo-5,6,7,8-tetrahydro-4H-chromene-4-carboxylate derivatives (4a-f) through a tandem Michael addition-cyclization reaction starting with structurally diverse cyclohexane-1,3-dione, diethyl acetylene dicarboxylate, and malononitrile has been carried out in different organic bases under solvent free condition for the optimization of maximum yield. All the formed 4H-chromenes were characterized by spectral and X-ray methods.     

Copper(I)-catalyzed cascade sulfonimidate to sulfonamide rearrangement: synthesis of imidazo[1,2-a][1,4]diazepin-7(6H)-one

A novel strategy of copper(I)-catalyzed cascade intramolecular nucleophilic attack on N-sulfonylketenimine followed by rearrangement of sulfonimidates to sulfonamides resulting in a library of substituted 8,9-dihydro-5H-imidazo[1,2-a][1,4]diazepin-7(6H)-ones has been developed.     

Catalytic oxidation and C–C coupling reactions of new ruthenium(III) Schiff base complexes containing PPh<Subscript>3</Subscript> or AsPh<Subscript>3</Subscript> co-ligands

New mononuclear ruthenium(III) Schiff base complexes of the type [RuX₂(EPh₃)(L)] (X = Cl or Br; E = P or As; L = monobasic tridentate Schiff base derived from o-aminophenol or o-aminothiophenol with ethylacetoacetate or ethylbenzoylacetate) have been synthesized. The Schiff base ligands chelate to ruthenium through O, N, and O/S by dissociation of the phenolic proton/thiophenolic proton forming chelate rings. These complexes have been characterized by physico-chemical and spectroscopic methods. Cyclic voltammetric data of all the complexes showed Ru(III)/Ru(IV) oxidation and Ru(III)/Ru(II) reduction within the range of 0–1.5 V and 0 to −1.5 V with respect to Ag/AgCl, respectively. The complexes were tested as catalysts in the oxidation of alcohols using molecular oxygen at ambient temperature, and also in C–C coupling reactions. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Effect of substitution of Fe3+ in CuCr2O4 matrix for the hydrogenation of nitrobenzene

The hydrogenation of nitrobenzene to aniline over reduced Cu(Fe_xCr_2–x)O₄ series of catalysts (where x=0, 0.2, 0.4, 0.6, 0.8 and 1.0) has been studied at 250°C in a fixed bed flow type reactor. All the catalysts were characterized by XRD, IR and DRS analysis and by measurements of electrical conductivity and surface area. The conversion of nitrobenzene to aniline is maximum over the catalysts with composition x=0.4. By comparing the results of reversible and irreversible adsorption of carbon monoxide with hydrogenation activity, it can be concluded that univalent copper at octahedral sites is more active for hydrogenation than metallic copper. The second cations [Cr(III) or Fe(III)] develop their catalytic activity by sharing anionic vacancies.     

Schiff’s base phenol-hydrazone derivatives as colorimetric chemosensors for fluoride ions

Two new chromogenic receptors 4-nitro-2-[(phenylhydrazoimino)methyl]phenol (1) and 4-nitro-2-[(4-nitrophenylhydrazoimino)methyl]phenol (2) containing a nitro group as a signalling unit and OH and NH groups as binding sites have been synthesized and characterized by spectroscopic techniques and XRD. Both receptors show colorimetric responses and UV-vis spectral changes in the presence of fluoride ions in organic solvents.     

Experimental analyses on heat transfer performance of TiO2–water nanofluid in double-pipe counter-flow heat exchanger for various flow regimes

Journal of Thermal Analysis and Calorimetry - Nanofluids are widely used in heat transfer applications. This article presents the effect of heat transfer and pressure drop of the TiO2–water...