Novel Lead(iv) Reagents for Carbon-Carbon Bond Formation

Moloney, Mark G.; Thompson, R. M.; Wright, E. H. M.

doi:10.1515/mgmc.1996.19.3.133

Cited by 11 publications

(2 citation statements)

References 17 publications

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“…20 In other work, we have also found that the chiral complexes 1-4 (Scheme 2) do not induce efficient asymmetry transfer in phenylation reactions of b-dicarbonyl substrates (Scheme 3 ; e.e. values in the range 4È12% are observed).20,21 This is surprising given the well documented8,9 mechanism of these phenylations which involves reductive elimination from the lead(IV) intermediate 5, produced by BÈPb transmetallation, followed by ligand exchange with the dicarbonyl nucleophile, a reaction which would be expected to be acutely sensitive to its surrounding ligand environment.…”

Section: Methodsmentioning

confidence: 92%

207Pb,13C and1H Nuclear Magnetic Resonance Studies of Lead(IV) Carboxylates in Solution

Claridge¹,

Nettleton²,

Moloney³

1997

Magn. Reson. Chem.

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Section: Methodsmentioning

confidence: 92%

207Pb,13C and1H Nuclear Magnetic Resonance Studies of Lead(IV) Carboxylates in Solution

Claridge¹,

Nettleton²,

Moloney³

1997

Magn. Reson. Chem.

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“…Redox catalysts , are used for the electrochemically controlled conversion of molecules via a redox process that, in the absence of the catalyst, would only react under much more extreme conditions to yield, if at all, the same amount and type of product. The Pb 4+/2+ redox couple is an example of a reagent with a broad spectrum of stoichiometric uses in organic chemistry , especially with recent advances in synthetically useful carbon−carbon coupling processes − and for which a recycling procedure, for example by electrochemical means under mild conditions at an electrode surface, would be highly desirable.…”

Section: Introductionmentioning

confidence: 99%

Mechanistic Aspects of the Electrocatalytic Oxidative Cleavage of 1,2-Diols by Electrogenerated Pb(IV)

Marken¹,

Squires²,

Alden³

et al. 1998

J. Phys. Chem. B

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The electrochemical oxidation of Pb(II) to Pb(IV) in acetonitrile solution containing benzoic acid and pyridine is possible at a basal-plane pyrolytic-graphite electrode and associated with a rapid ligand exchange at the metal center. The Pb(IV) species generated under these conditions is shown to react with diols such as 1,2:5,6-di-O-isopropylidene-D-mannitol, 1,2-ethanediol, cis-and trans-1,2-cyclopentanediol, which undergo a two-electron oxidation associated with carbon-carbon bond cleavage. Voltammetric data obtained by both channel flow cell and rotating disk electrode experiments are analyzed by numerical simulation. Consistent results for a second-order EC′ (electrocatalytic) reaction pathway were obtained. Voltammetric data obtained by systematically varying the concentration of pyridine and benzoic acid reveal a complex mechanism with a distinct trend in reaction rate for each diol expressed in terms of apparent fractional reaction orders when analyzed in terms of a chemically oversimplified EC′ mechanism. This behavior is given mechanistic significance by analysis of the data using numerical simulation employing the following "branched" EC rev C rev C irrev ′ reaction scheme, which allows all the experimental results to be rationalized (benz ) benzoic acid, py ) pyridine): Pb(II) a Pb(IV) + 2e -; Pb(IV)(benz) h (py) i + diol a Pb(IV)(benz) h (diol)(py) i with rate constants k 1 and k -1 for the forward and reverse reactions, respectively; Pb(IV)(benz) h+j (diol)(py) i-k + k(py) a Pb(IV)(benz) h (diol)(py) i + j(benz) with rate constants k 2 and k -2 for the forward and reverse reactions, respectively; Pb(IV)(benz) h (diol)(py) i f Pb(II) + products with rate constant k f . Here, the chemical processes are associated with appropriate rate constants, k n , and the equilibrium constant of a process is given by K n ) k n /k -n (n ) 1, 2). The "true" second-order rate constants K 1 k f obtained for the electrocatalytic cleavage of 1,2:5,6-di-O-isopropylidene-D-mannitol (k ) j ) 1),56) × 10 3 M -1 s -1 are similar to within 1 order of magnitude. The effect of the diffusion of coexisting species coupled via fast preequilibria to the irreversible chemical process is discussed in respect to the physical meaning of the rate constants determined by applying a simplified mechanistic scheme.

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The First [4+2]-Coordinated Tetraorganolead Compound: Synthesis, Structure and Conversion into a Triorganolead Cation, a Benzoxaphosphaplumbole, and Diorganolead Dihalides

Peveling

Schürmann

Jurkschat

2002

Z. anorg. allg. Chem.

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The syntheses and molecular structures, as determined by single-crystal X-ray diffraction analysis, of the first intramolecularly [4ϩ2]-coordinated tetraorganolead compound {4-t-Bu-2,6-[P(O)(OEt) 2 ] 2 C 6 H 2 }PbPh 3 (2) and the triphenyllead chloride adduct of the first intramolecularly coordinated benzoxaphosphaplumbole {[1(Pb),3(P)-Pb(Ph) 2 OP(O)(OEt)-5-t-Bu-7-P(O)-(OEt) 2 ]C 6 H 2 ·Ph 3 PbCl} (3a) are reported. The reaction of 2 with [Ph 3 C] ϩ [PF 6 ] Ϫ and p-MeC 6 H 4 SO 3 H, respectively, provides the

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Novel Lead(iv) Reagents for Carbon-Carbon Bond Formation

Cited by 11 publications

References 17 publications

207Pb,13C and1H Nuclear Magnetic Resonance Studies of Lead(IV) Carboxylates in Solution

207Pb,13C and1H Nuclear Magnetic Resonance Studies of Lead(IV) Carboxylates in Solution

Mechanistic Aspects of the Electrocatalytic Oxidative Cleavage of 1,2-Diols by Electrogenerated Pb(IV)

The First [4+2]-Coordinated Tetraorganolead Compound: Synthesis, Structure and Conversion into a Triorganolead Cation, a Benzoxaphosphaplumbole, and Diorganolead Dihalides

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