Rate and Mechanism of the Oxidative Addition of Benzoic Anhydride to Palladium(0) Complexes in DMF

The rate constant of the oxidative addition of the benzoic anhydride (PhCO)2O to [Pd0(PPh3)4] has been determined in DMF and compared to that of phenyl halides and phenyl triflate. The following reactivity order has been established: PhI >> (PhCO)2O > PhOTf > PhBr. The oxidative addition of (PhCO)2O proceeds by activation of one C−O bond. Two acyl-PdII complexes are formed: a neutral complex trans-[(PhCO)Pd(OCOPh)(PPh3)2] and a cationic complex trans-[(PhCO)PdS(PPh3)2]+ (S = DMF) showing that the decarbonylation process is highly endergonic. The exchange of PPh3 by the bidentate ligand dppp does not favor the decarbonylation process.

Oxidative Addition To Platinum(ii) Complexes

This thesis describes the oxidative addition of alcohols, water and organic halides to dimethyl(2,2-bipyridine)platinum(II) (complex (I)) and to dimethyl(1,10-phenanthroline)platinum(II) (complex (II)). The work has involved characterising the reaction products and investigating the mechanism of oxidative addition. Up to now very little mechanistic work has been done for oxidative addition at platinum(II) centres.;Complexes (I) and (II) react with methanol, ethanol and isopropanol to produce the first series of platinum(IV) alkoxides of general formula {lcub}PtMe(,2)(OR)(N N)H(,2)O{rcub}(\u27+){lcub}OH{rcub}(\u27-) (N N = bipy or phen; R = Me, Et, (\u27i)Pr). Characterisation was achieved by (\u271)H nmr, (\u2713)C nmr and elemental analysis. In an analogous reaction with water the product was a platinum(IV) hydroxo complex.;Primary organic halides reacted cleanly with complex (II) to produce complexes of general formula {lcub}PtXMe(,2)(R)(phen){rcub} (X = I or Br; R = Me, Et, (\u27n)Pr, (\u27n)Bu). The reactions proceed via an S(,N)2 mechanism.;The reaction of complex (II) with methylene dihalides is believed to proceed via the intermediacy of free-radicals. The reaction of CH(,2)X(,2) (X = Cl, Br or I) with (II) produced a mixture of cis- and trans-isomers of general formula {lcub}PtXMe(,2)(CH(,2)X)(phen){rcub}. Complex (II) reacted with CH(,2)ClI producing a mixture of platinum(IV) complexes, which involved halogen scrambling.;The reaction of X(CH(,2))(,2)X (X = I or Br) with (II) is thought to proceed via competing radical chain and radical non-chain mechanisms. The novel binuclear complexes {lcub}Pt(,2)X(,2)Me(,4){lcub}(CH(,2))(,2){rcub}(phen)(,2){rcub} were isolated from these reactions.;The reaction of (II) with an excess of the (alpha),(omega)-diiodoalkanes I(CH(,2))(,n)I (n = 3-5) produced mononuclear complexes of general formula {lcub}PtIMe(,2){lcub}(CH(,2))(,n)I{rcub}(phen){rcub}. The reaction proceeds via an S(,N)2 mechanism. These mononuclear complexes reacted further with (II), also via an S(,N)2 mechanism to produce the binuclear bridging polymethylene complexes, {lcub}Pt(,2)I(,2)Me(,4){lcub}(CH(,2))(,n){rcub}(phen){rcub}. The rate-constants for these reactions could be measured and indicate a neighbouring atom effect for the reaction of the complexes, {lcub}PtIMe(,2){lcub}(CH(,2))(,n)I{rcub}(phen){rcub}, with (II). In deoxygenated solvent isopropyl iodide reacted with (II) to form {lcub}PtIMe(,2)((\u27i)Pr)(phen){rcub}. However, in the presence of dioxygen the major product was {lcub}PtIMe(,2)((\u27i)PROO)(phen){rcub}. This is the first platinum(IV)peroxo complex to be isolated and a single crystal x-ray structure was performed for this complex. . . . (Author\u27s abstract exceeds stipulated maximum length. Discontinued here with permission of author.) UM

Photoinitiated oxidative addition of CF3I to gold(I) and facile aryl-CF3 reductive elimination.

Herein we report the mechanism of oxidative addition of CF3I to Au(I), and remarkably fast Caryl-CF3 bond reductive elimination from Au(III) cations. CF3I undergoes a fast, formal oxidative addition to R3PAuR (R = Cy, R = 3,5-F2-C6H4, 4-F-C6H4, C6H5, 4-Me-C6H4, 4-MeO-C6H4, Me; R = Ph, R = 4-F-C6H4, 4-Me-C6H4). When R = aryl, complexes of the type R3PAu(aryl)(CF3)I can be isolated and characterized. Mechanistic studies suggest that near-ultraviolet light (λmax = 313 nm) photoinitiates a radical chain reaction by exciting CF3I. Complexes supported by PPh3 undergo reversible phosphine dissociation at 110 °C to generate a three-coordinate intermediate that undergoes slow reductive elimination. These processes are quantitative and heavily favor Caryl-I reductive elimination over Caryl-CF3 reductive elimination. Silver-mediated halide abstraction from all complexes of the type R3PAu(aryl)(CF3)I results in quantitative formation of Ar-CF3 in less than 1 min at temperatures as low as -10 °C

Synthesis of γ-lactones from alkenes employing p-methoxybenzyl chloride as +CH2---CO−2 equivalent

The ZnCl2 catalyzed reaction of p-methoxybenzyl chloride with alkenes yields the 1:1 addition products 3, which are converted into the γ-lactones 4 via Ru(VIII) catalyzed oxidative degradation of the aromatic ring

Clinical relevance of biomarkers of oxidative stress

SIGNIFICANCE Oxidative stress is considered to be an important component of various diseases. A vast number of methods have been developed and used in virtually all diseases to measure the extent and nature of oxidative stress, ranging from oxidation of DNA to proteins, lipids, and free amino acids. Recent Advances: An increased understanding of the biology behind diseases and redox biology has led to more specific and sensitive tools to measure oxidative stress markers, which are very diverse and sometimes very low in abundance. CRITICAL ISSUES The literature is very heterogeneous. It is often difficult to draw general conclusions on the significance of oxidative stress biomarkers, as only in a limited proportion of diseases have a range of different biomarkers been used, and different biomarkers have been used to study different diseases. In addition, biomarkers are often measured using nonspecific methods, while specific methodologies are often too sophisticated or laborious for routine clinical use. FUTURE DIRECTIONS Several markers of oxidative stress still represent a viable biomarker opportunity for clinical use. However, positive findings with currently used biomarkers still need to be validated in larger sample sizes and compared with current clinical standards to establish them as clinical diagnostics. It is important to realize that oxidative stress is a nuanced phenomenon that is difficult to characterize, and one biomarker is not necessarily better than others. The vast diversity in oxidative stress between diseases and conditions has to be taken into account when selecting the most appropriate biomarker. Antioxid. Redox Signal. 00, 000-000

Oxidative Addition Reactions Of Dimethylplatinum(ii) Complexes

This work deals with synthesis, characterization and reaction mechanisms in studies of the oxidative addition of organic compounds to dimethyl(1,10-phenanthroline)-platinum(II), (PtMe{dollar}\sb2{dollar}(NN)). The organic compounds studied include lactones, epoxides, alkylpalladium(IV) complexes, alkyl halides including a coumarin derivative, and diphenyl diselenide and diphenyl disulphide. A particularly detailed study has been made of the oxidative addition of the C-O bonds of a {dollar}\beta{dollar}-lactone and of epoxides.;The oxidative addition of propiolactone to the platinum(II) complex to give a platina(IV)lactone, (PtMe{dollar}\sb2\{lcub}{dollar}CH{dollar}\sb2{dollar}CH{dollar}\sb2{dollar}C(O)O{dollar}\{rcub}{dollar} (NN)), (NN = 2,2{dollar}\sp\prime{dollar}-bipyridine or 1,10-phenanthroline) is reported. The structure is determined by both NMR and X-ray crystallography. The oxidative addition of propiolactone to the platinum(II) complex is deduced to follow an S{dollar}\sb{lcub}\rm N{rcub}{dollar}2 type mechanism.;The oxidative addition of some simple epoxides to the complex (PtMe{dollar}\sb2{dollar}(NN)) in the presence of carbon dioxide is shown to give platinacarbonate complexes. The rate-determining step in the reaction is the oxidative addition of the epoxide to (PtMe{dollar}\sb2{dollar}(NN)) and a dipolar intermediate, (Me{dollar}\sb2{dollar}(NN)Pt{dollar}\sp+{dollar}CH{dollar}\sb2{dollar}CHRO{dollar}\sp-{dollar}), is formed through nucleophilic attack by platinum(II) on the least substituted carbon atom of the epoxide, CH{dollar}\sb2{dollar}CHRO. The rapid insertion of CO{dollar}\sb2{dollar} then occurs to give the stable cyclic metallacarbonate products.;A study of reactivity, selectivity and mechanism in alkyl halide transfer reactions from palladium(IV) to platinum(II) complexes was carried out. Kinetic studies have shown that the major route involves loss of halide from palladium(IV) in a preequilibrium step, followed by S{dollar}\sb{lcub}\rm N{rcub}{dollar}2 attack by (PtMe{dollar}\sb2{dollar}(NN)) on an alkyl group (PdMe{dollar}\sb3{dollar}(NN)) {dollar}\sp+{dollar} or (PdMe{dollar}\sb2{dollar}(CH{dollar}\sb2{dollar}Ph)(NN)) {dollar}\sp+{dollar}.;The oxidative addition reactions of O-O, S-S and Se-Se bonds to (PtMe{dollar}\sb2{dollar}(NN)) to give the corresponding platinum(IV) complexes have also been studied and the products have been characterized by NMR as (PtMe{dollar}\sb2{dollar}(OH){dollar}\sb2{dollar}(NN)) or (PtMe{dollar}\sb2{dollar}(EPh){dollar}\sb2{dollar}(NN)), E = S or Se. The oxidative addition of 4-bromomethyl-7-methoxycoumarin to the dimethylplatinum complex yields a fluorescent platinum(IV) complex and the oxidative addition of allyl chloride and bromoacetyl chloride to (PtMe{dollar}\sb2{dollar}(NN)) are also described briefly. (Abstract shortened by UMI.

Uranium-mediated oxidative addition and reductive elimination

This Perspective article summarises the emerging research topic of uranium-mediated oxidative addition and reductive elimination.</p

Visible light-mediated gold-catalysed carbon(sp2)-carbon(sp) cross-coupling.

A dual photoredox and gold-catalysed cross-coupling reaction of alkynyltrimethylsilanes and aryldiazonium tetrafluoroborates is described. The reaction proceeds through visible-light mediated oxidative addition of aryldiazoniums, transmetalation of alkynyltrimethylsilanes and aryl-alkynyl reductive elimination. Exclusive selectivity for silyl-substituted alkynes is observed, with no reactivity observed for terminal alkynes