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Ring Closure (ring + closure)
Terms modified by Ring Closure Selected AbstractsRing Closure of Alkoxycarbonyl(tetracarbonyl)pyruvoyliron Complexes into Metallalactones Induced by Nucleophilic Attack of CarbanionsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2006Patrice Cabon Abstract The reaction of carbanions with the pyruvoyl-substituted iron complex [(CO)4Fe(CO2CH3){C(O)C(O)CH3}] (1) affords the anionic trifunctionalized metallalactones [(CO)3Fe{C(O)C(CH3)(CRR,R,)OC4(O)(Fe,C4)}(CO2CH3)], (3), whose formation results from the addition of the nucleophile to the , carbonyl of the pyruvoyl moiety, followed by attack of the oxygen of this , carbonyl on a terminal carbonyl ligand. These anionic lactones react, at low temperature, with HCl to give rise to the neutral lactones [(CO)4Fe{C(O)C(CH3)(CRR,R,)OC4(O)(Fe,C4)}] (2), which were previously obtained by addition of NuH nucleophiles to 1. Complex 3(3), whose lactonic ring formation has been performed using the diethyl malonate anion (R = R, = CO2C2H5; R, = H), and the dimethyl-substituted neutral lactone 2(1) (R = R, = R, = H) have been characterized by X-ray diffraction studies. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Synthesis of Highly Functionalized , -Lactones via 1,5-Electrocyclic Ring ClosureHELVETICA CHIMICA ACTA, Issue 6 2006Olcay Anaç Abstract We have investigated 1,5-electrocyclic ring-closure reactions of conjugated esters with dimethyl diazomalonate in the presence of [Cu(acac)2] as catalyst. Our new protocol offers an easy entry to various polyfunctionalized , -lactones in high yields. Their subsequent derivatives may be used as valuable intermediates, especially in the synthesis of natural products and their analogues. [source] ChemInform Abstract: Preparation of Phthalamic Acid Derivatives and Ring Closure to Phthalimidobarbituric Acids.CHEMINFORM, Issue 13 2008Agnieszka Ambrozak Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Preference of 4-exo Ring Closure in Copper-Catalyzed Intramolecular Coupling of Vinyl Bromides with Alcohols.CHEMINFORM, Issue 45 2007Yewen Fang Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] A New Approach to the Nazarov Reaction via Sequential Electrocyclic Ring Opening and Ring Closure.CHEMINFORM, Issue 48 2006Tina N. Grant Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Furan Ring Opening,Furan Ring Closure: Cascade Rearrangement of Novel 4-Acetoxy-9-furylnaphtho[2,3-b]furans.CHEMINFORM, Issue 39 2006Vladimir V. Mel'chin Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] A New Synthesis of 4H-1,4-Benzothiazine Derivatives Based on Ring Closure of EWG-Stabilized (2-Isocyanophenylthio)methyl Anions.CHEMINFORM, Issue 30 2006Kazuhiro Kobayashi Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Furan Ring Opening,Isochromene Ring Closure: A New Approach to Isochromene Ring Synthesis.CHEMINFORM, Issue 11 2006Alexander V. Butin Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Synthesis of Benzo[b]furans via CuI-Catalyzed Ring Closure.CHEMINFORM, Issue 1 2006Cheng-yi Chen Abstract For Abstract see ChemInform Abstract in Full Text. [source] Regioselective Aryl Radical Cyclization: Access to Pyrimidine-Anellated Spiro Heterocycles Through 5-exo Ring Closure.CHEMINFORM, Issue 1 2005K. C. Majumdar Abstract For Abstract see ChemInform Abstract in Full Text. [source] Novel Generation and Ring Closure of 1,3-Thiaza-1,3-butadiene S-Oxides Through Thermal Cycloreversion of 6H-1,3,5-Oxathiazine S-Oxides.CHEMINFORM, Issue 26 2003Kazuaki Shimada Abstract For Abstract see ChemInform Abstract in Full Text. [source] A New Entry to Carbocycles: Synthesis of Cyclopentene and Cyclohexene Derivatives Through endo-Mode Ring Closure of Allenyl Sulfones.CHEMINFORM, Issue 20 2003Chisato Mukai Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Stereoselective Synthesis of (E)-4-Alkylidenecyclopent-2-en-1-ones by a Tandem Ring Closure,Michael Addition,Elimination.CHEMINFORM, Issue 33 2001Roberto Ballini Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] A Radical Version of the Bromo- and the Iodocyclization of Bis(homoallylic) Alcohols , The Synthesis of Halogenated Tetrahydrofurans by Stereoselective Alkoxyl Radical Ring ClosuresEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2003Jens Hartung Abstract A new synthesis of bromo- and iodomethyl-substituted tetrahydrofurans has been devised. The sequence starts with the conversion of aryl-functionalized bis(homoallylic) alcohols 1 into N -alkenoxythiazole-2(3H)-thiones 6 or pyridine-2(1H)-thiones 7. When photolyzed in the presence of appropriate trapping reagents, thiones 6 and 7 efficiently liberated substituted 4-penten-1-oxyl radicals 2, which underwent synthetically useful 5- exo -trig cyclizations. Cyclized radicals 3 were trapped with BrCCl3 or an adequate iodine atom donor (either n -C4F9I or diethyl 2-iodo-2-methyl malonate) to provide halocyclization products 4 or 5. This strategy has been applied for the synthesis of 3-, 4-, or 5-phenyl-substituted 2-(1-bromo-1-methylethyl)tetrahydrofurans 4a,c (75,90%, 36,96% de), which were not attainable as major products from polar, for example NBS-mediated, bromocyclizations. Aryl-substituted 2-iodomethyl tetrahydrofurans 5 (46,80%) were prepared in a similar way starting from N -alkenoxypyridine-2(1H)-thiones 7 and a suitable iodine atom donor. Diastereomerically pure iodides cis - 5 and trans - 5 served as starting materials for a stereochemical analysis of disubstituted tetrahydrofurans by NMR spectroscopy and X-ray diffraction analysis. The results of this investigation clarified that all new alkoxyl radical cyclizations followed in terms of regio- and diastereoselectivity the general guidelines which had been established for this type of ring-closure reaction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Peptide-Embedded Heterocycles by Mild Single and Multiple Aza-Wittig Ring Closures.CHEMINFORM, Issue 30 2007Matthias Riedrich Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] A Radical Version of the Bromo- and the Iodocyclization of Bis(homoallylic) Alcohols , The Synthesis of Halogenated Tetrahydrofurans by Stereoselective Alkoxyl Radical Ring Closures.CHEMINFORM, Issue 7 2004Jens Hartung No abstract is available for this article. [source] A novel three-component one-pot reaction involving ,-naphthol, aldehydes, and urea promoted by TMSCl/NaIJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 2 2010Gowravaram Sabitha Amidoalkyl naphthol derivatives have been synthesized in good yields in a one-pot condensation of ,-naphthol, aromatic aldehydes and urea in presence of TMSCl/NaI at room temperature. Ring closure of amidoalkyl naphthol derivatives occurred at 140°C to afford 1,2-dihydro-1-arylnaphtho[1,2-e] [1,3]oxazin-3-one derivatives. J. Heterocyclic Chem., (2010). [source] Synthesis and reactions of 3-amino-2-methyl-3H -[1,2,4]triazolo[5,1- b]-quinazolin-9-one and 2-hydrazino-3-phenylamino-3H -quinazolin-4-oneJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 6 2003Mohamed A. Saleh The reaction of 3- N -(2-mercapto-4-oxo-4H -quinazolin-3-yl)acetamide (1) with hydrazine hydrate yielded 3-amino-2-methyl-3H -[1,2,4]triazolo[5,1- b]quinazolin-9-one (2). The reaction of 2 with o -chlorobenzaldehyde and 2-hydroxy-naphthaldehyde gave the corresponding 3-arylidene amino derivatives 3 and 4, respectively. Condensation of 2 with 1-nitroso-2-naphthol afforded the corresponding 3-(2-hydroxy-naphthalen-1-yl-diazenyl)-2-methyl-3H -[1,2,4]triazolo[5,1- b]quinazolin-9-one (5), which on subsequent reduction by SnCl2 and HCl gave the hydrazino derivative 6. Reaction of 2 with phenyl isothiocyanate in refluxing ethanol yielded thiourea derivative 7. Ring closure of 7 subsequently cyclized on refluxing with phencyl bromide, oxalyl dichloride and chloroacetic acid afforded the corresponding thiazolidine derivatives 8, 9 and 10, respectively. Reaction of 2-mercapto-3-phenylamino-3H -quinazolin-4-one (11) with hydrazine hydrate afforded 2-hydrazino-3-phenylamino-3H -quinazolin-4-one (12). The reactivity 12 towards carbon disulphide, acetyl acetone and ethyl acetoacetate gave 13, 14 and 15, respectively. Condensation of 12 with isatin afforded 2-[N -(2-oxo-1,2-dihydroindol-3-ylidene)hydrazino]-3-phenylamino-3H -quinazolin-4-one (16). 2-(4-Oxo-3-phenylamino-3,4-dihydroquinazolin-2-ylamino)isoindole-1,3-dione (17) was synthesized by the reaction of 12 with phthalic anhydride. All isolated products were confirmed by their ir, 1H nmr, 13C nmr and mass spectra. [source] Azide,Tetrazole Ring-Chain Isomerism in Polyazido-1,3,5-triazines, Triazido- s -heptazine, and DiazidotetrazinesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2006Anton Hammerl Abstract The azide,tetrazole isomerism in several polyazido-1,3,5-triazines, triazido- sym -heptazine, and some diazido-1,2,4,5-tetrazines was investigated by ab initio quantum chemical methods in order to determine whether the polyazides are suitable starting materials for the synthesis of the isomeric tetrazoles. The effects of solvation in CCl4, DMSO and water on this isomerism were included using the self consistent reaction field (SCRF) method. The effect of amino- and nitrosubstituents on the azide,tetrazole isomerism was also examined. In the gas phase all investigated polyazidoheterocycles do not cyclize to form tetrazoles. An electron-donating amino group favors the ring closure to tetrazoles, whereas an electron-withdrawing nitro group favors the azides. Solvation in polar solvents favors the formation of a tetrazole ring system due to higher charge separation in the tetrazole ring system, but for all polyazido-1,3,5-triazines, including triazido- s -heptazine, the effects of solvation are not strong enough to shift the equilibrium to the tetrazole side, which explains why several attempts to detect these compounds have failed. The monotetetrazoles of diazidotetrazine and bis(azido)azo-1,2,4,5-tetrazine and the ditetrazole of bis(azido)hydrazo-1,2,4,5-tetrazine are the minimum energy species in DMSO and water. Thus we predict that the diazidoazo- and hydrazotetrazines will readily cyclize to the tetrazoles in polar solvents. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] First (Peroxo)vanadium(V) Complex with Heteroligand Formed in Reaction System , Synthesis, Structure and Reactivity of K[VO(O2)(omeida)]·H2O {omeida = N -[2-(2-oxomorpholine-4-yl)ethyl]iminodiacetato(2,)}EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2003Michal Sivák Abstract The crystalline peroxo complex of vanadium(V), K[VO(O2)(omeida)]·H2O, where omeida is a ,-lactone derivative, N -[2-(2-oxomorpholine-4-yl)ethyl]iminodiacetate(2,), has been obtained by reaction of vanadate with H2O2 and N -(2-hydroxyethyl)ethylenediaminetriacetic acid (HEDTA) in acidic aqueous solution at pH = 3 and 278 K. X-ray analysis revealed a distorted pentagonal-bipyramidal coordination around the vanadium atom, with a typical cis arrangement of oxo and peroxo ligands in apical and equatorial positions, respectively. Two amino nitrogen atoms of the tetradentate omeida(2,)-N1,N2,O1,O2 ligand occupy the neighbouring equatorial positions of the pentagonal plane, and two oxygen atoms of carboxymethyl groups bound to the same N1 nitrogen atom are in equatorial and apical positions. The six-membered lactone ring in omeida was formed in the reaction solution from carboxy and hydroxy groups not involved in coordination with the vanadium atom. The 51V NMR spectra of K[VO(O2)(omeida)]·H2O, and of peroxovanadate/HEDTA/H2O and vanadate/HEDTA/H2O solutions, as well as the 1H NMR spectrum of HEDTA, proved that lactone ring closure proceeds only in peroxovanadate but not vanadate solutions. Spectroscopic investigation of the oxygen transfer reaction from the peroxo ligand in [VO(O2)(omeida)], to the thiolato sulfur atom in [Co(en)2{S(CH2)2NH2}]2+ or [Co(en)2(cyst)]+, and of the oxidation of N -acetyl- L -cysteine by K[VO(O2)(omeida)]·H2O, revealed much more complicated reaction mechanisms than those of other (amino-polycarboxylato)monoperoxo complexes of vanadium(V). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Dihydroazulene Photoswitches: The First Synthetic Protocol for Functionalizing the Seven-Membered RingEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2009Michael Åxman Petersen Abstract The first synthetic protocol for functionalizing the dihydroazulene (DHA) photoswitch in its seven-membered ring has been developed. This protocol is based on regioselective bromination, followed by regioselective elimination of HBr, and finally a palladium-catalyzed cross-coupling reaction with a terminal alkyne. The position of functionalization (C-7) was confirmed by X-ray crystal structure analysis. Light-induced ring opening of this compound to its vinylheptafulvene (VHF) isomer followed by thermal ring closure provides a mixture of two DHA regioisomers in a ratio that depends on the wavelength of irradiation and solvent polarity.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Asymmetric Synthesis of (S)-Mirtazapine: Unexpected Racemization through an Aromatic ipso -Attack MechanismEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2008Marco van der Linden Abstract An asymmetric synthesis of (S)-mirtazapine has been achieved from the synthesis of the racemate by using (S)-1-methyl-3-phenylpiperazine as the starting material. Unfortunately, significant racemization was encountered in the final step, which involved an electrophilic aromatic ring closure of a alcohol by concentrated sulfuric acid. A significantly higher ee was observed when polyphosphoric acid (PPA) was used instead. A remarkable correlation between the amount of PPA used and the ee of the product was revealed, namely, an increase in the ee upon decreasing the amount of PPA. This trend was paralleled by the formation of an increasing amount of a side-product upon lowering the amount of PPA. The racemization and formation of a side-product can be explained by an ipso -attack mechanism during the electrophilic aromatic ring-closure reaction. This mechanism was supported by a mechanistic study using a deuterium-labeled substrate.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Synthesis of Tyrosine-Derived Tetrahydroisoquinolines by Lewis Acid Catalyzed Cyclization of N -(Phenylsulfonyl)alkyloxazolidinones,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 33 2007Stefan Tussetschläger Abstract N -Boc-protected tyrosine esters 5a,b were converted into tetrahydroisoquinolines 13 and 14 in four steps by reduction and ring closure to oxazolidinones 9 and 10, addition of benzenesulfinic acid and aldehydes to sulfones 11 and 12 and subsequent Lewis acid catalyzed cyclization. In the case of m -tyrosine derivative 5a, selective protection with bromine prevented the formation of undesired regioisomers. Debromination of target compounds 13 was readily achieved under radical reduction conditions by using Bu3SnH/AIBN. Tetrahydroisoquinolines 13 and 14 were isolated as single diastereomers whose trans configuration was confirmed by X-ray crystal structure analysis. Partial epimerization of trans - 13i and trans - 21 to the corresponding cis diastereomers was achieved under basic conditions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Synthesis of Enantiopure 1-Azaspiro[4.5]decanes by Iodoaminocyclization of AllylaminocyclohexanesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 18 2007Faïza Diaba Abstract The 5- endo iodine-promoted ring closure of 4-allyl-4-(alkylamino)cyclohexanone derivatives gives the corresponding 1-azaspiro[4.5]decanes in good yields. The reaction was tested with enantiopure homoallylamines to evaluate the diastereoselectivity of the process and to provide a route for possible intermediates to the natural products embodying this azabicyclic ring.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Concave Imidazolinium Salts as Precursors to Concave N-Heterocyclic Carbenes,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 6 2007Ole Winkelmann Abstract Concave bimacrocyclic imidazolinium ions 8 have been synthesized as precursors for N-heterocyclic carbenes 9 (NHC) in 13 to 29,% overall yields based on 2-nitroresorcinol (1). As bridgeheads, 2,6-bis(,-alkenyloxy)anilines 3 have been synthesized from 1. Reaction of 3 with oxalyl chloride, reduction to respective diamines 5, and ring closure with triethyl orthoformate gave N,N -diaryl-substituted imidazolinium ions 6. The terminal vinyl groups were connected by ring-closing metathesis to give bimacrocyclic imidazolinium ions 7, whose alkene functions were hydrogenated to give saturated bimacrocyles 8. The structure of 8a was elucidated by X-ray analysis. The respective NHC 9 was generated by deprotonation with potassium tert -butoxide, and 9 was scavenged with CS2 to give adduct 10. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Asymmetric Synthesis of ,,,-Substituted ,-Sultones via Allylation of Chiral Lithiated SulfonatesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2003Dieter Enders Abstract The first auxiliary controlled asymmetric synthesis of enantiopure ,,,-substituted ,-sultones via ,-allylation of lithiated sulfonates by using 1,2:5,6-di- O -isopropylidene-,- D -allofuranose as chiral auxiliary is described. The high asymmetric inductions of the ,-allylations were reached in good to excellent yields. Successive epimerization-free cleavage of the auxiliary and diastereoselective ring closure of the sulfonic acid intermediates in a one-pot procedure led to the title compounds in good to excellent yields and diastereo- and enantiomeric excesses (de, ee , 98%). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Formal Synthesis of Olivacine via IndolylborateHELVETICA CHIMICA ACTA, Issue 10 2008Minoru Ishikura Abstract Palladium-catalyzed tandem cyclization,cross-coupling reaction of indolylborate 2 and vinyl bromide 5 was successfully applied in a short formal synthesis of olivacine. The reaction of 2 with 5 in the presence of Pd(OAc)2 readily afforded three kinds of products, triene derivative 6 and vinylindole derivative 7, along with a small amount of the piperidine derivative 8 (Scheme,2). On the other hand, the reactions of 2 with bromide 10 or 15 were also examined (Schemes,4 and 5), and their outcome markedly depended on the relative ease of ring closure as a function of ring size. Irradiation of 6 with a high-pressure mercury lamp (,9; Scheme,2), followed by removal of the N -[(benzyloxy)carbonyl] group and subsequent oxidation afforded, after deprotection, pyridocarbazole 23, and the conversion of 23 to olivacine is known (Scheme,6). [source] Metal Complexes of Functionalized Sulfur-Containing Ligands.HELVETICA CHIMICA ACTA, Issue 7 2003Part XIX The title compounds were prepared starting from the dihydropyrrolones 4,6. Nucleophilic displacement and ring closure yielded the 1H -pyrrolo[3,2- c]isothiazol-5(4H)-ones 8 and 10. The fused systems formed salts with strong acids and electrophiles (15, 16), as well as with bases. Oxidation led either to S(2)-oxides (18a, 20a) or to the corresponding bicyclic sultams (18b, 20b), depending on the reaction conditions. The sulfinamide 18a was also obtained from the known 1,2-dithiolopyrrolone S -oxide 21 by a ring-opening/ring-closure reaction sequence. O -Methylation of 8 furnished the ,azafulvene' 17. The oxidative addition of [Pt(,2 -C2H4)L2] (24a: L=Ph3P, 24b: L=1/2,dppf, 24c: L=1/2,(R,R)-diop) to 18a and 20a led to the cis -amido-sulfenato Pt complexes 25 and 26a,c, respectively. [source] Facile synthesis of 3-spiroindolinesHETEROATOM CHEMISTRY, Issue 3 2002Yehia A. Allam Cyanoacetyldiazoindol-2-one (3), the condensation product of cyanoacetohydrazide with isatin (1), could be cyclized in acidic medium via its CN group and its enolic OH to give cyanomethyloxadiazole-spiroindoline (4). The presence of the methylcyano side chain could be invested,through oximation, diazotization, or condensation with aldehydes,to form polyfunctional spiroindolines 5, 8,10. Also, a second route for preparing the title compound could be achieved through a nucleophilic attack on position 3 in the isatin derivatives, followed by subsequent ring closure to give 6 and 7. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:207,210, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10020 [source] The reactivity of Ni(II) toward aspartic and glutamic monohydroxamatesINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 9 2006Fawzia Al-Sogair The formation of complexes of Ni(II) with aspartic and glutamic acid hydroxamates was determined by potentiometric methods at I = 0.15 M NaCl and T = 25°C. The equilibrium study of Ni(II) with ASX or GLX revealed that the predominant species formed in solution were (M:L:H+): (1:1:0), (1:1:1), (2:1:0), and (2:1:1) in the whole pH range (,3,11). The formation of polymeric species was not observed. The octahedral structures were predicted in which the ligands act as tridentate ligands. The kinetics of complex formation between Ni(II) with ASX system as well as Ni(II) with GLX were also studied in a wide pH range. The observed rate constants for the Ni(II)-hydroxamates were found to be dependent on the total concentration of hydroxamates at a given pH through the following relations: kobs = Y0 + Z(TASX) and kobs = Y0 + Z(TGLX) + W(TGLX)2. The trans effect of the hydroxyl group present in the reacting species of Ni(OH)+ as well as a ring closure resulted from ligand chelation are introduced as explanations for the rate constants obtained for the reactions of Ni(II) with ASX or GLX. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 540,552, 2006 [source] | ||||||||||||||||||||||||||||