Ambidenticity of a tridentate oxygen-nitrogen donor towards bivalent and trivalent transition metal ions

Summary N-salicylidene anthranilamide (H₂SAA) and its Cr^III, Mn^II, Fe^III, Co^II, Ni^II and Cu^II complexes were prepared and characterized by physicochemical and spectroscopic data. H₂SAA enolizes to give a dibasic ONO donor set in the divalent metal complexes. It also binds to the trivalent metal ions in a nonenolized form using a monobasic ONN donor set. Co^II is oxidized to Co^III during complexation. Octahedral geometries are proposed for Cr^III, Mn^II, Fe^III and Co^III complexes, while square planar geometries are suggested for the Ni^II and Cu^II complexes. Phenoxide bridging in the Cr^III and Fe^III complexes and enoxide bridging in the Ni^II and Cu^II complexes is proposed.     

Microwave‐assisted regioselective one‐pot synthesis of trisubstituted pyridine scaffolds using K5CoW12O40.3H2O under solvent free conditions

A highly efficient, microwave‐assisted, regioselective synthesis of 2,3‐disubstituted‐6‐arylpyridines and new series of 7,7‐dimethyl‐2‐aryl‐5,6,7,8‐tetrahydroquinoline‐5‐ones from enaminones in the presence of K₅CoW₁₂O₄₀.3H₂O (1.0 mol %) as heterogeneous catalyst under solvent free conditions is reported.     

Fluorescent aluminum chelate complexes as modified precursors for nano-structured alumina

A series of new mononuclear heteroleptic derivatives of aluminum(III), {[(CH₃COCHCOCH₃)AlL] (1 and 4)}, {[(C₆H₅COCHCOC₆H₅)AlL] (2, 5, and 7)}, and {[(C₉H₆NO)AlL] (3 and 6)}, have been synthesized by reacting Al(OPrⁱ)₃ with tridentate Schiff base H₂L^x (H₂L¹ = C₁₃H₁₀BrNO₂; H₂L² = C₁₄H₁₃NO₃; H₂L³ = C₁₇H₁₃NO₂) and β-diketone/8-hydroxyquinoline (β-diketone = acetylacetone/dibenzoylmethane) in 1?:?1?:?1 stoichiometry using anhydrous benzene and ethanol. All the complexes were characterized by elemental analysis, FTIR, and NMR (¹H and ¹³C) spectral studies. Molecular structures obtained from single-crystal XRD of aqua 1 (1a) and DMSO coordinated 2 (2a) authenticate their existence. Further, nanostructured α-alumina was synthesized from 1 by well-established sol–gel method and was characterized by powder XRD, TEM, and EDX analyses.     

Iodine-catalyzed efficient synthesis of azaarene substituted 3-hydroxy-2-oxindole derivatives through sp3 C–H functionalization

Iodine-catalyzed benzylic sp³ C–H bond functionalization of lutidines or picolines to isatins is described. This synthetic method provides a rapid entry towards biologically interesting 3-azaarene substituted 3-hydroxy-2-oxindole derivatives.     

A highly efficient regioselective one-pot synthesis of 2,3,6-trisubstituted pyridines and 2,7,7-trisubstituted tetrahydroquinolin-5-ones using K5CoW12O40·3H2O as a heterogeneous recyclable catalyst

A systematic investigation into the regioselective one-pot, three-component condensation of enaminones 1a–g, β-dicarbonyl compounds 2a–c, and ammonium acetate in the presence of a catalytic amount of K₅CoW₁₂O₄₀·3H₂O (0.01 equiv or 1.0 mol %) under solvent free conditions, as well as in refluxing isopropanol, has been reported. The reaction was highly efficient to produce 2,3,6-trisubstituted pyridines 3a–g, 4a–g, and novel 2,7,7-trisubstituted-5,6,7,8-tetrahydroquinoline-5-ones 5a–g in excellent yields. The present procedure offers advantages of short reaction time, simple work-up, and the catalyst exhibited remarkable reusable activity.     

Structural elucidation of manganese(II), iron(III), cobalt(II), nickel(II), copper(II) and zinc(II) complexes of a new multidentate dihydrazino quinoxaline derivative

Summary Manganese(II), iron(III), cobalt(II), nickel(II), copper(II) and zinc(II) complexes of a new multidentate oxygen-nitrogen donor, bis(N-salicylidene)-2,3-dihydrazino-1,4-quinoxaline (H₂BSDHQ) were prepared and characterised by elemental analysis, conductance, thermal, spectral and magnetic data. H₂BSDHQ deprotonates to give a dibasic ONNO donor set in a trivalent iron(III) complex, which binds to the divalent metal ions in a bis-tridentate fashion, using two monobasic ONN donor sets, and resulting in polymeric complexes. Octahedral geometries are proposed for all these complexes, and preliminary studies show that they possess potential antimicrobial activity.