- Solution equilibrium, structural and cytotoxicity studies on Ru(η6-p-cymene) and copper complexes of pyrazolyl thiosemicarbazones
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Solution chemical properties of two bidentate pyrazolyl thiosemicarbazones 2-((3-methyl-1-phenyl-1H-pyrazol-4-yl)methylene)hydrazinecarbothioamide (Me-pyrTSC), 2-((1,3-diphenyl-1H-pyrazol-4-yl)methylene)hydrazinecarbothioamide (Ph-pyrTSC), stability of their Cu(II) and Ru(η6-p-cymene) complexes were characterized in aqueous solution (with 30% DMSO) by the combined use of UV–visible spectrophotometry, 1H NMR spectroscopy and electrospray ionization mass spectrometry in addition to their solid phase isolation. The solid phase structures of Me-pyrTSC?H2O, [Ru(η6-p-cymene)(Me-pyrTSC)Cl]Cl and [Cu(Ph-pyrTSCH?1)2] were determined by single crystal X-ray diffraction. High stability mononuclear Ru(η6-p-cymene) complexes with (N,S) coordination mode are formed in the acidic pH range, and increasing the pH the predominating dinuclear [(Ru(η6-p-cymene))2(L)2]2+ complex with μ2-bridging sulphur donor atoms is formed (where L? is the deprotonated thiosemicarbazone). [CuL]+ and [CuL2] complexes show much higher stability compared to that of complexes of the reference compound benzaldehyde thiosemicarbazone. [CuL2] complexes predominate at neutral pH. Me-pyrTSC and Ph-pyrTSC exhibited moderate cytotoxicity against human colonic adenocarcinoma cell lines (IC50 = 33–76 μM), while their complexation with Ru(η6-p-cymene) (IC50 = 11–24 μM) and especially Cu(II) (IC50 = 3–6 μM) resulted in higher cytotoxicity. Cu(II) complexes of the tested thiosemicarbazones were also cytotoxic in three breast cancer and in a hepatocellular carcinoma cell line. No reactive oxygen species production was detected and the relatively high catalase activity of SUM159 breast cancer cells was decreased upon addition of the ligands and the complexes. In the latter cell line the tested compounds interfered with the glutathione synthesis as they decreased the concentration of this cellular reductant.
- D?m?t?r, Orsolya,Kiss, Márton A.,Gál, G. Tamás,May, Nóra V.,Spengler, Gabriella,Nové, Márta,Ga?parovi?, Ana ?ipak,Frank, éva,Enyedy, éva A.
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- An iron(iii)-catalyzed dehydrogenative cross-coupling reaction of indoles with benzylamines to prepare 3-aminoindole derivatives
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We report a green cascade approach to prepare a variety of 3-aminoindole derivatives in good to excellent yields through an iron(iii)-catalyzed dehydrogenative cross-coupling reaction of 2-arylindoles and primary benzylamines under mild reaction conditions. Mechanistic studies show that a cascade reaction involves a tert-butyl nitrite (TBN)-mediated nitrosation of 2-substituted indoles and a 1,5-hydrogen shift to afford indolenine oximes, sequential iron(iii)-catalyzed condensation and a 1,5-hydrogen shift over four steps in a one-pot reaction. The reaction shows a broad substrate scope of indoles and benzylamines and tolerates a wide range of functional groups. Moreover, the reaction is easily performed at the gram scale without producing waste after the reaction is completed. The 3-aminoindole product is purified by simple extraction, washing, and recrystallization without flash column chromatography. A double imine ligand containing the 3-aminoindole unit is facile to obtain in a 52% yield in one step. The present method highlights readily available starting materials, a simple purification procedure, and the usage of cheap, nontoxic, and environmentally benign iron(iii) catalysts. This journal is
- Chen, Wei-Li,Li, Kun,Liang, Cui,Liang, Wang-Fu,Liao, Wei-Cong,Mo, Dong-Liang,Qiu, Pei-Wen,Su, Gui-Fa
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supporting information
p. 9610 - 9616
(2021/12/09)
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- Shaken, not stirred: a schools test for aldehydes and ketones
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A schools test for aldehydes and ketones in water at room temperature using test tubes has been developed in this laboratory using either phenylhydrazine hydrochloride or phenylhydrazine hydrochloride with NaOAc . 3H2O. The role of one equivalent of a strong or weak acid which catalyses the reaction is discussed.
- Plater, M John
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p. 104 - 107
(2019/11/22)
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- Simple and efficient approach for synthesis of hydrazones from carbonyl compounds and hydrazides catalyzed by meglumine
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A simple, environmentally benign protocol for synthesis of hydrazones from carbonyl compounds and hydrazides has been developed in the presence of meglumine in aqueous-ethanol media at room temperature. The salient features of the present protocol are mild reaction conditions, short reaction time, high yields, operational simplicity, metal-free, applicability toward large-scale synthesis, and biodegradable and inexpensive catalyst.
- Zhang, Mo,Shang, Ze-Ren,Li, Xiao-Tang,Zhang, Jia-Nan,Wang, Yong,Li, Kang,Li, Yang-Yang,Zhang, Zhan-Hui
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p. 178 - 187
(2017/01/10)
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- TEMPO-mediated Aza-diels-alder reaction: Synthesis of tetrahydropyridazines using ketohydrazones and olefins
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A novel, facile, and efficient method for the synthesis of tetrahydropyridazines by a one-pot tandem reaction of easily accessible ketohydrazones and olefins in the presence of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) has been successfully developed. The reaction involves the initial generation of azoalkenes from direct oxidative dehydrogenation of ketohydrazones using TEMPO as the commercially available oxidant, followed by a subsequent aza-Diels-Alder reaction with olefins.
- Yang, Xiu-Long,Peng, Xie-Xue,Chen, Fei,Han, Bing
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supporting information
p. 2070 - 2073
(2016/06/09)
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- Spontaneous dehydrogenation of 2-hydrazinoethyl- and 4-hydrazinobut-2- enylphosphonium salts
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2-Hydrazinoethyl- and 4-hydrazinobut-2-enylphosphonium salts undergo spontaneous dehydrogenation leading to the corresponding hydrazones or diazenes, depending on the structure of the starting compounds or the reaction conditions. A possible mechanism of the trans-formations is discussed.
- Ovakimyan,Gasparyan,Movsisyan,Grigoryan
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p. 2338 - 2343
(2013/10/01)
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- Autoxidation of hydrazones. Some new insights
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(Chemical Equation Presented) Autoxidation of hydrazones is a generally occurring reaction, leading mostly to the formation of α- azohydroperoxides. All structural kinds of hydrazones, having at least one hydrogen atom on nitrogen, are prone to autoxidation; however, there are marked differences in the rate of the reaction. Hydrazones of aliphatic ketones are 1-2 orders of magnitude more reactive than analogous derivatives of aromatic ketones. Even less reactive are the hydrazones of chalcones, which function also as efficient inhibitors of autoxidation of other hydrazones. These differences can be attributed to the reduction of the rate of the addition of oxygen to a hydrazonyl radical, which is a reversible reaction. In the case of conjugated ketones, it becomes endothermic, making this elementary step slow down and the chain termination reactions become important. Substituents influence the stability of hydrazonyl radicals and, consequently, the bond dissociation energies of the N-H bonds. In acetophenone phenylhydrazones, the substituents placed on the ring of hydrazine moiety exhibit a higher effect (Hammett ρ = -2.8) than those on the ketone moiety (ρ = -0.82), which denotes higher importance of the structure with spin density concentrated on nitrogen in delocalized hydrazonyl radical. Electronic effects of the substituents also affect the transition state for the abstraction of hydrogen atom by electrophilic peroxy radicals; NBO analysis display a negative charge transfer of about 0.4 eu from hydrazone to a peroxy radical in the transition state.
- Harej, Maja,Dolenc, Darko
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p. 7214 - 7221
(2008/02/11)
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- Photorearrangement of α-azoxy ketones and triplet sensitization of azoxy compounds
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(Chemical Equation Presented) Although some aspects of azoxy group radical chemistry have been investigated,1 unhindered α-azoxy radicals remain poorly understood. Here we report the generation of α-azoxy radicals under mild conditions by irradiation of α-azoxy ketones 4a,b. These compounds undergo α-cleavage to yield radicals 5a,b, whose oxygen atom then recombines with benzoyl radicals to produce presumed intermediate 15. Formal Claisen rearrangement gives α-benzoyloxyazo compounds 8a,b, which are themselves photolabile, leading to both radical and ionic decomposition. The ESR spectrum of 5a was simulated to extract the isotropic hyperfine splitting constants, which showed its resonance stabilization energy to be exceptionally large. Azoxy compounds have been found for the first time to be good quenchers of triplet excited acetophenone, the main sensitized photoreaction of 7Z in benzene being deoxygenation. While this reaction has been reported previously, it was always in hydrogen atom donating solvents, where chemical sensitization occurred. The principal direct irradiation product of 4bZ and model azoxyalkane 7Z is the E isomer, whose thermal reversion to Z is much faster than that of previously studied analogues.
- Engel, Paul S.,Tsvaygboym, Konstantin P.,Bachilo, Sergei,Smith, William B.,Jiang, JinJie,Chignell, Colin F.,Motten, Ann G.
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p. 2598 - 2605
(2007/10/03)
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- Electrochemical formation of methoxy- and cyano(phenylazo)alkanes from aldehyde and ketone phenylhydrazones
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Several aldehyde and ketone phenylhydrazones were electrooxidized in MeOH. Electrooxidation in the presence of KI or tetraethylammonium p-toluenesulfonate as the supporting electrolyte afforded the corresponding methoxy(phenylazo)alkanes, whereas electrooxidation in the presence of KI, NaCN, and HOAc afforded the cyano(phenylazo)alkanes.
- Okimoto, Mitsuhiro,Takahashi, Yukio,Kakuchi, Toyoji
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p. 2057 - 2063
(2007/10/03)
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- Thermolysis of Geminal Bisazoalkanes. Stabilization of a Carbon-Centered Radical by the Azo Substituent
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Two geminal bisazoalkanes (1 and 2) have been employed to generate a radical center next to the azo group.The 8.0 kcal/mol lower ΔG(excit.) for thermolysis of 1 and 2 relative to model compounds 6 and 7 is dissected into a 1 kcal/mol contribution from ground state elevation of 1 and 2 and at least 2.6 kcal/mol from phenyl stabilization of radical 3.Any extra stabilization of the aliphatic 2,3-diazaallyl radical (4) relative to α,α-dimethylallyl amounts to no more than 4.4 kcal/mol.Finally, γ-phenyl conjugation of the α,α-dimethylallyl radical stabilizes it by 4.5 kcal/mol.
- Engel, Paul S.,Wang, Chengrong,Chen, Yan-Qiu,He, Shu-Lin,Andrews, B. Kim,Weisman, R. Bruce
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p. 6257 - 6261
(2007/10/02)
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- Reduction of Azoalkanes by Benzhydryl Radicals
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Benzhydryl radicals donate a hydrogen atom rapidly to the less hindered nitrogen atom of aliphatic and aromatic azo compounds, leading to the corresponding hydrazines.When the initially formed hydrazyl radical posseses a weak β-bond, it undergoes scission before receiving a second hydrogen atom.Thermolysis of benzpinacol with azocyclopropane causes a complex rearrangement to 1,5-diazaoct-5-en-1-yne (21).
- Engel, Paul S.,Wu, Wen-Xue
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p. 1830 - 1835
(2007/10/02)
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- Rate constants for abstraction of bromine from bromotrichloromethane by butyl, cyclopropylmethyl, and phenyl radicals in solution
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The radical chain decomposition of cyclopropylmethyl(1-hydroxy-1-methylethyl)diazene ((CH3)2C(OH)N=NCH2- 1) at 253-341 K in hexafluorobenzene or in dichloromethane solution containing bromotrichloromethane affords cyclopropylmethyl bromide, 4-bromo-1-butene, 1-bromo-5,5,5-trichloro-2-pentene, and 3,5-dibromo-1,1,1-trichloropentane from the cyclopropylmethyl portion of 1.Other major products are nitrogen, acetone, and chloroform.The rate constant for formation of cyclopropylmethyl bromide by attack of cyclopropylmethyl free radicals from 1 at bromine of BrCCl3 (kBrcpm) was calculated from the product composition using the known rate constant for rearrangement of cyclopropylmethyl radicals to 3-buten-1-yl radicals.At 25 deg C, kBrcpm = 6.5 x 1E8 M-1s-1 and the temperature dependence is given by log (kBrcpm/M-1s-1) = (10.6 +/- 0.3) - (2.4 +/- 0.4)/θ, where θ = 2.3RT kcal/mol-1.Non-chain decomposition of (CH3)2C(OH)N=N-R (2, R = Bu, and 3, R = Ph) in the presence of excess 1,1,3,3-tetramethylisoindolin-2-yloxyl (4) and bromotrichloromethane afforded BuBr and PhBr, respectively, in yields determined by the relative concentrations of 4 and BrCCl3.Rate constants for coupling (kc) of Bu. and Ph. with 4 were assumed to be proportional to rate constants for diffusion controlled reactions, kd, which were estimated from measured viscosities.Values of kBrBu and kBrPh, calculated from kc and product yields for reactions at 80 deg C, are 0.26 x 1E9 and 1.55 x 1E9 M-1s-1, respectively.The relative radical reactivities toward BrCCl3 at 80 deg C are Ph, 6; cpm, 5; Bu, 1.
- Mathew, Lukose,Warkentin, John
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- Four- and Five-membered Phosphorus Heterocycles, 63 - 1,2,3?2-Diazaphosphole Chemistry - 4-Bromo and 4-Thio Derivatives
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Diazaphospholes are not oxidized by bromine at the phosphorus atom.The 4-unsubstituted representatives 1a, b are instead (preferentially with the help of a base) converted to the 4-bromo derivatives 2a, b.All involved and observed single reaction steps are 1,2-additions and 1,2-eliminations (of Br2 or HBr) at the PC bond.In the same sense 1a reacts with the disulfide, bromine, and triethylamine to give the 4-(methylthio)- and 4-(phenylthio)diazaphospholes 8c and 8a.
- Hoegel, Johann,Schmidpeter, Alfred
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p. 1621 - 1631
(2007/10/02)
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- ALKALINE ISOMERIZATION OF PHENYLHYDRAZONES TO ALKYLPHENYLDIIMIDES
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When solutions pf phenylhydrazones in tri- or tetraethylene glycol are heated in the presence of the corresponding sodium glycolate, they undergo isomerization to alkylphenyldiimidates.There is a marked decrease in the isomerization rate in the transition from the hydrazones of aldehydes to the hydrazones of ketones.With the phenylhydrazones of ketones the reaction takes place almost unambiguously, but in the case of hydrazones of aldehydes it is complicated to an appreciable extent by side processes such as indolization and aminonitrile cleavage.
- Kuznetsov, M.A.,Suvorov, A.A.
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p. 1684 - 1691
(2007/10/02)
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- Synthesis, spectral and structural studies, and an evaluation of the hydrogen bonding of some phenylhydrazones
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A series of 46 phenylhydrazones, some novel, containing a variety of structural types has been synthesised. These have been studied by 1H n.m.r. and i.r. spectroscopy with respect to potential inter- and intra-molecular hydrogen bonding. ortho-Nitro or -carbonyl groups form strong hydrogen bonds to the imino-group which are readily observed by 1H n.m.r. but not by i.r. spectroscopy. 'Terminal' carbonyl groups also form strong hydrogen bonds to the imino-group and these can be detected by both i.r. and 1H n.m.r. spectroscopy. When both ortho-nitro- or -carbonyl groups and 'terminal' carbonyl groups are present the imino hydrogen atom is doubly hydrogen bonded and this is apparent in the 1H n.m.r. spectrum. The formation of an intramolecular hydrogen bond in the phenylhydrazone prevents the formation of an intermolecular hydrogen bond between the phenylhydrazone and a polar solvent.
- Kaberia, Festus,Vickery, Brian,Willey, Gerald R.,Drew, Michael G. B.
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p. 1622 - 1626
(2007/10/02)
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