Microwave Assisted Conversion of Oximes and Semicarbazones to Carbonyl Compounds Using Benzyltriphenylphosphonium Peroxymonosulfate

Summary.  Benzyltriphenylphosphonium peroxymonosulfate in the presence of catalytic amounts of bismuth chloride was found to be an efficient and mild reagent for the oxidative cleavage of oximes and semicarbazones to the corresponding carbonyl compounds under microwave irradiation. Corresponding author. E-mail: haji@cc.iut.ac.ir Received March 4, 2002; accepted (revised) April 8, 2002     

Semicarbazones and thiosemicarbazones,XII: Crystal structure of salicylaldehyde semicarbazone

Summary The crystal and molecular structure of salicylaldehyde semicarbazone was obtained by single crystal X-ray diffraction. The O atom of the semicarbazone fragment isanti to the N atom of the hydrazinic group. The distribution of bond lengths in the semicarbazone fragment indicates delocalization of the -electrons. The crystal structure is stabilized by intra- and intermolecular hydrogen bonds.

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Semicarbazone und Thiosemicarbazone, 12. Mitt.: Die Kristallstruktur des Salicylaldehyd-Semicarbazons

Zusammenfassung Die Kristallstruktur und die molekulare Struktur des Salicylaldehyd-Semicarbazons wurde über Einkristall-Röntgenstreuung ermittelt. Das O-Atom des Semicarbazonteils stehtanti zum N-Atom der Hydrazin-Gruppierung. Die Bindungslängen in der Semicarbazoneinheit zeigen eine Delokalisierung der -Elektronen an. Die Geometrie der Verbindung wird durch stabilisierende intra- und intermolekulare Wasserstoffbrückenbindungen bestimmt.

     

Synthesis, spectral characterization and crystal structure of copper(II) complexes of 2-benzoylpyridine-N(4)-phenylsemicarbazone

An interesting series of nine new copper(II) complexes [Cu₂L₂(OAc)₂]·H₂O (1), [CuLNCS]·½H₂O (2), [CuLNO₃]·½H₂O (3), [Cu(HL)Cl₂]·H₂O (4), [Cu₂(HL)₂(SO₄)₂]·4H₂O (5), [CuLClO₄]·½H₂O (6), [CuLBr]·2H₂O (7), [CuL₂]·H₂O (8) and [CuLN₃]·CH₃OH (9) of 2-benzoylpyridine-N(4)-phenyl semicarbazone (HL) have been synthesized and physico-chemically characterized. The tridentate character of the semicarbazone is inferred from IR spectra. Based on the EPR studies, spin Hamiltonian and bonding parameters have been calculated. The g values, calculated for all the complexes in frozen DMF, indicate the presence of the unpaired electron in the d_x²-y² orbital. The structure of the compound, [Cu₂L₂(OAc)₂] (1a) has been resolved using single crystal X-ray diffraction studies. The crystal structure revealed monoclinic space group P2₁/n. The coordination geometry about the copper(II) in 1a is distorted square pyramidal with one pyridine nitrogen atom, the imino nitrogen, enolate oxygen and acetate oxygen in the basal plane, an acetate oxygen form adjacent moiety occupies the apical position, serving as a bridge to form a centrosymmetric dimeric structure.     

A DFT study of molecular structures and tautomerizations of 2-benzoylpyridine semicarbazone and picolinaldehyde N-oxide thiosemicarbazone and their complexations with Ni(II), Cu(II), and Zn(II)

The structure optimizations of picolinaldehyde N-oxide thiosemicarbazone (Hpiotsc), 2-benzoylpyridine semicarbazone (H2BzPS), their imino tautomers and their complexes with Ni(II), Cu(II), and Zn(II) were carried out using DFT calculations. The structures of Hpiotsc and H2BzPS ligands, transition states of their tautomerizations were obtained at the B3LYP/6-31+G(d,p) level and their thermodynamic properties were derived from the frequency calculations at the same level of theory. The B3LYP/LANL2DZ-optimized structures of Hpiotsc and H2BzPS complexes with Ni(II), Cu(II), and Zn(II), and the thermodynamic properties of their complexations derived from the B3LYP/LANL2DZ-frequency calculations were obtained. The B3LYP/LANL2DZ-optimized geometrical parameters for the [Ni(Hpiotsc)₂]²⁺, [Cu(Hpiotsc).Cl₂], and [Zn(Hpiotsc).Cl₂] complexes show good agreement with their corresponding X-ray crystallographic data.     

Synthesis and Characterization of Chloralose-Derived Thiosemicarbazones and Semicarbazones and Investigation of Their Antimicrobial Properties

Thiosemicarbazones(7–10)/semicarbazones(11–14) were synthesized in good yields via the condensation of α-gluco-, β-gluco-, galacto-, manno- chloralose derived 1,4-furanodialdoses (1-4) with thiosemicarbazide(5)/semicarbazide(6). The structures of all products were characterized by FTIR, NMR spectroscopic methods and elemental analysis. The compounds have been found to display moderate antimicrobial activity against Gram-positive, Gram-negative bacteria and antifungal activity against a Candida albicans. MIC values of the compounds range from 260 to 1510 μg/mL.     

Deprotection of Oximes,Phenylhydrazones, Semicarbazones and Thiosemicarbazones to the Corresponding Carbonyl Compounds Using Cetyltrimethylammonium Peroxodisulfate as a New and Selective Oxidizing Agent

Cetyltrimethylammonium peroxodisulfate (CTA)₂S₂O₈ was quantitatively prepared and used for the deprotection of oximes, phenylhydrazones, semicarbazones and thiosemicarbazones to the corresponding carbonyl compounds in acetonitrile. Its agent is more efficient and has advantages over similar reagents in terms of the amount of oxidant, short reaction time, simple work up, and high yield.     

Synthesis and crystal structure of a two-dimensional bi-layered supramolecular network compound [Cu2(C7H8N4O)4](ClO4)2 (C7H8N4O=pyridine-3-carbaldehyde semicarbazone)

A two-dimensional bi-layered supramolecular compound [Cu₂(C₇H₈N₄O)₄](ClO₄)₂ has been synthesized by the solvothermal method, and characterized via IR and CHN elemental analysis. The single crystal X-ray data of this compound reveal the complex to be dimeric as a result of terminal –NH₂ group of the semicarbazone moiety bridging, which is relatively rare. On this bi-copper(I) complex, another remarkably structural feature is that each Cu atom adopts an unsymmetrical T-shaped geometry comprised of three N atoms from three pyridine-3-carbaldehyde semicarbazone ligands. The molecules are linked into a two-dimensional bi-layered framework by intermolecular N–H?···?O hydrogen bonds.     

Synthesis of novel steroidal oxazolo quinoxaline as antibacterial agents

Steroidal[oxazolo(4,5-b)quinoxaline-2-yl-hydrazone] derivative (7a–9a) (7b–9b) were prepared by the multi-step reactions of steroid. It is prepared via the reaction of steroidal semicarbazones with 2,3-dichloroquinoxaline at 80 °C in ethanol. The structures of the compounds were evident by IR, ¹H NMR and mass spectrometry and their purities were confirmed by elemental analyses. The antibacterial activity of these compounds was evaluated by the disk diffusion assay against two Gram-positive and two Gram-negative bacteria and then the minimum inhibitory concentration (MIC) of compounds was determined. The results showed that compounds (7a, 7b, 8a, 8b) are better antibacterial agent as compared with the standard drug amoxicillin.     

Synthesis,crystal structures,antimicrobial activities,and DFT calculations of two new azido nickel(II) complexes

Two new complexes, [Ni(HL¹)(N₃)(μ_1,1N₃)]₂ (1) [HL¹: NC₅H₄CH₃C=NNH (C=O) NH₂] and [Ni(L²)N₃] (2) [HL²: NC₅H₄HC=N NH(C=S)NH₂], have been synthesized by reaction of Ni(OAC)₂·4H₂O and sodium azide with HL¹ and HL² and characterized by elemental analysis, FT-IR, and UV–vis spectral studies. Single-crystal X-ray diffraction reveals that 1 is dinuclear with nickel(II) in an octahedral environment of NNO donors of HL¹, two nitrogens of azide bridges and one nitrogen of terminal azide; 2 is mononuclear containing nickel(II) in a distorted square-planar environment of NNS donors of HL² and one terminal azide. The structures of 1 and 2 have been optimized by density functional theory. The results of antimicrobial activities of ligands, 1 and 2 demonstrated that HL² and 2 have good antimicrobial activity in contrast with HL¹ and 1, related to the presence of sulfur donor in HL².     

Tetracyanoquinodimethane Derivatives of Pentagonal Bipyramidal Complexes of Manganese(II), Iron(II), Nickel(II) and Copper(II) with 2,6-diacetylpyridinebis(semicarbazone)∶ Single Crystal Structure of dichloro[2,6-diacetylpyridinebis (semicarbazone)] Manganese(II)monohydrate

By using the donor ligand 2,6-diacetylpyridinebis(semicarbazone) (DAPSC), pentagonal bipyramidal complexes of Mn(II), Fe(II), Ni(II) and Cu(II) have been obtained. The structure of [MnCl₂(DAPSC)]·H₂O has been determined by X-ray crystallography. Further reactions of these complexes with lithium salts of 7,7',8,8'-tetracyanoquinodimethane (TCNQ) yielded their corresponding adducts.