Evidence of Desulfurization in the Oxidative Cyclization of Thiosemicarbazones. Conversion to 1,3,4-Oxadiazole Derivatives

Gómez-Saiz, Patricia; García–Tojal, Javier; Maestro, Miguel A.; Arnáiz, Francisco J.; Rojo, Teófilo

doi:10.1021/ic015625s

Cited by 69 publications

(47 citation statements)

References 13 publications

(10 reference statements)

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“…Other reported oxidation processes show the appearance of sulfate groups, which arise from oxidation of the thione sulfur atom [43] or desulfurisation of the thiosemicarbazonecopper(II) system by transformation of the thioamide group into a nitrile. [44] All of these processes explain the versatility of thiosemicarbazone skeletons in supplying new organic and inorganic systems.…”

Section: X-ray Diffraction Studiesmentioning

confidence: 99%

Metal‐Catalysed Oxidation Processes in Thiosemicarbazones: New Complexes with the Ligand N‐{2‐([4‐N‐Ethylthiosemicarbazone]methyl)phenyl}‐p‐toluenesulfonamide

Pedrido¹,

Romero²,

Bermejo³

et al. 2007

Chemistry A European J

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The coordination behaviour of a new thiosemicarbazone Schiff-base building block, N-{2-([4-N-ethylthiosemicarbazone]methyl)phenyl}-p-toluenesulfonamide, H2L1 (1), incorporating a bulky tosyl group, towards Mn II, Fe II, Co II, Ni II, Cu II, Zn II, Cd II, Ag I, Sn II, and Pb II has been investigated by means of an electrochemical preparative procedure. Most metal complexes of L1 have the general formula [M(L1)]2.nX (M=Mn, Fe, Co, Ni, Cu, Cd, Pb; n=0-4, X=H2O or CH3CN), as confirmed by the structure of [Pb(L1)]2 (15), in which the lone pair on lead is stereochemically active. This lead(II) complex shows an intense fluorescence emission with a quantum yield of 0.13. In the case of silver, the complex formed was found to possess a stoichiometry of [Ag2(L1)]2.3H2O. During reactions with manganese and copper metals, interesting catalysed processes have been found to take place, with remarkable consequences regarding the ligand skeleton structure. In synthesising the manganese complex, we obtained an unexpected dithiolate thiosemicarbazone tosyl ligand, H2L2, as a side-product, which has been fully characterised, including by X-ray diffraction analysis. In the case of copper, the solid complex has the formula [CuL1]2, but the crystallised product shows the copper atoms coordinated to a new cyclised thiosemicarbazone ligand, H2L3, as in the structures of the complexes [Cu(L3)]2.CH3CN (8) and [Cu(L3)(H2O)]2.CH3CN.H2O (9). The zinc complex [Zn(L1)]4 (12) displays a particular tetranuclear zeolite-type structure capable of hosting small molecules or ions, presumably through hydrogen bonding.

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Section: X-ray Diffraction Studiesmentioning

confidence: 99%

Metal‐Catalysed Oxidation Processes in Thiosemicarbazones: New Complexes with the Ligand N‐{2‐([4‐N‐Ethylthiosemicarbazone]methyl)phenyl}‐p‐toluenesulfonamide

Pedrido¹,

Romero²,

Bermejo³

et al. 2007

Chemistry A European J

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“…Excess acid and too much heat have led to brown solutions from which crystals of bis(pyridinecarboxylate)copper() were isolated. [17] Ligand 8 can be removed from 6 by the addition of K 4 [Fe(CN) 6 ]·3H 2 O in ethanol. Furthermore, it can also be synthesized by direct oxidative cyclization of HL I mm.…”

Section: The Oxidation Processmentioning

confidence: 99%

“…[17] The singularity of this reaction lies not only in the fact that 1,3,4-oxadiazoles are obtained from a nonϪacylated substrate for the first time, but in the novel process of desulfurization of thiosemicarbazones that implies this oxidative cyclization. The usual methods of preparing oxadiazoles consist of the cyclization of substrates such as acyl thiosemicarbazides [18] or acyl thioureas [19,20] with a variety of oxidants.…”

Section: Introductionmentioning

confidence: 99%

New 1,3,4‐Oxadiazolecopper(II) Derivatives Obtained from Thiosemicarbazone Complexes

et al. 2003

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Pyridine‐2‐carbaldehyde thiosemicarbazone and pyridine‐2‐carbaldehyde 4N‐methyl thiosemicarbazone ligands (HLI and HLImm respectively) undergo an oxidative cyclization when treated with bromate or iodate, leading to 2‐amino‐5‐pyridin‐2‐yl‐1,3,4‐oxadiazole and 2‐methylamino‐5‐pyridin‐2‐yl‐1,3,4‐oxadiazole (HLII and HLIImm). This reaction occurs either with free ligands or when coordinated to copper(II). Some of the starting ([{Cu(LImm)(NO3)}2] (3), intermediate Cu(LI)(IO3)·(H2O) (1), [{Cu(LI)I}2] (2), [{Cu(LImm)Br}2] (4), and final compounds [{Cu(HLII)(H2O)3}2](SO4)2 (5), [{Cu(HLIImm)(H2O)2(SO4)}2]·2H2O (6), (HLII) (7), [HLIImm]·3H2O (8) have been isolated and characterized by elemental analyses, IR, UV‐visible, NMR, and EPR spectroscopy. The structures of 2, 3, 4, 5, 6, and 8, solved by X‐ray diffraction methods, contain dinuclear entities with either square‐pyramidal (2, 3, 4) or octahedral (5, 6) copper(II) ions. Structural and spectroscopic results suggest that ligand‐to‐metal charge transfer occurs in these compounds. The EPR spectra at 120 K exhibit rhombic (1, 3, 4), isotropic (2), and axial (5, 6) signals. Magnetic measurements show antiferromagnetic couplings for 2, 4, 5, and 6. The susceptibility data were fitted by the Bleaney−Bowers equation for copper(II) dimers. The obtained J/k values are −20.20, −8.85, −2.75, and −2.78 K for 2, 4, 5, and 6, respectively. However, ferromagnetic intradimeric interactions are present in 3 (J/k = +9.90 K) together with antiferromagnetic interdimer coupling (z′J′/k = −1.70 K). Magneto‐structural studies show the influence of the non‐thiosemicarbazone coligand in the magnetic behaviour of these complexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

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“…Some of them are the oxidative cyclizations of acyl hydrazones, acyl thioureas and acyl thiosemicarbazides 14 .…”

Section: Introductionmentioning

confidence: 99%

Synthesis, Characterization and Study of Thermal, Magnetic and Electrical Properties of Transition Metals Complexes of Some Newly Synthesized 2, 5-Substituted Oxadiazoles

Wanale¹,

Pachling²,

Deosarkar³

2013

Chem Sci Trans

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This paper reports the synthesis and characterization of transition metal complexes of newly synthesized 2,5-substituted-1,3,4-oxadiazoles with Cu(II), VO(IV), Ni(II), Zn(II) and Cd(II). The characterization of complexes were done by elemental analysis, UV-Vis, IR, ESR methods as well as the electrical conductance, magnetic susceptibility and thermal studies. The thermal behaviour provided confirmation of the complex composition as well as the number and the nature of water molecules and the intervals of thermal stability. The in vitro qualitative and quantitative antimicrobial activity assay of all the complexes was carried out.

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Evidence of Desulfurization in the Oxidative Cyclization of Thiosemicarbazones. Conversion to 1,3,4-Oxadiazole Derivatives

Cited by 69 publications

References 13 publications

Metal‐Catalysed Oxidation Processes in Thiosemicarbazones: New Complexes with the Ligand N‐{2‐([4‐N‐Ethylthiosemicarbazone]methyl)phenyl}‐p‐toluenesulfonamide

Metal‐Catalysed Oxidation Processes in Thiosemicarbazones: New Complexes with the Ligand N‐{2‐([4‐N‐Ethylthiosemicarbazone]methyl)phenyl}‐p‐toluenesulfonamide

New 1,3,4‐Oxadiazolecopper(II) Derivatives Obtained from Thiosemicarbazone Complexes

Synthesis, Characterization and Study of Thermal, Magnetic and Electrical Properties of Transition Metals Complexes of Some Newly Synthesized 2, 5-Substituted Oxadiazoles

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