Organolead(IV) Tricarboxylates, New Reagents for Organic Synthesis

Pinhey, JT

doi:10.1071/ch9911353

Cited by 82 publications

(21 citation statements)

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“…Lead(IV) reagents find considerable application in organic synthesis and have been found to mediate both oxidative processes (Rubottom, 1982) and C---C bondforming reactions (Pinhey, 1991;Abramovitch, Barton & Finet, 1988;Barton, 1990). We have been interested in extending the synthetic applications of lead(IV) reagents and to this end are investigating the synthesis, characterization and reactivity of a wide range of lead(IV) tetracarboxylates.…”

Section: Commentmentioning

confidence: 99%

Tetrakis(o-benzoylbenzoato-O,O')lead(IV) Dichloromethane Solvate

Prout¹,

Vaughan-Lee²,

Moloney³

et al. 1996

Acta Crystallogr C

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In the title complex, [Pb(CI4H903)4].CH2CI..2, the Pb atom is located at a point of symmetry (4) and is coordinated by eight carboxylate O atoms of four benzoylbenzoate anions at the corners of a somewhat distorted trigonal dodecahedron [Pb---O 2.317 (9) and 2.235 (9)A]. The dichloromethane solvent molecule is disordered in holes in the crystal structure, on the fourfold inversion axis between the Pb atoms.

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Section: Commentmentioning

confidence: 99%

Tetrakis(o-benzoylbenzoato-O,O')lead(IV) Dichloromethane Solvate

Prout¹,

Vaughan-Lee²,

Moloney³

et al. 1996

Acta Crystallogr C

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“…Its reaction with sodium hydride and acetyl chloride yielded a mixture of the 2-acetyl and 2,2diacetyl derivatives 11 (52%) and 12 (46%). Use of ptolyllead triacetate, 14 an aryl cation equivalent, 15 as the electrophile led to the diarylated derivative 13 in modest yield (22%), together with unreacted starting material. 16 In both cases, the tendency towards introduction of two molecules of the electrophile must be attributed to the electron-withdrawing nature of the groups introduced at C 2 , which favors deprotonation of the monosubstituted derivative through proton exchange with the anion of 1.…”

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confidence: 99%

A General Synthesis of Quinoline-2,5,8(1H)-triones via Acylation of 2,5-Dimethoxyaniline with S-tert-Butyl Thioacetates by Application of the Knorr Cyclization

López‐Alvarado¹,

Avendaño²,

Menéndez³

1998

Synthesis

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An efficient synthesis of quinoline-2,5,8(1H)-triones bearing alkyl groups at C 3 and/or C 4 is described. The reaction sequence employed involves Knorr cyclization of 2,5-dimethoxyanilides into 5,8-dimethoxyquinoline systems, followed by oxidative demethylation with cerium ammonium nitrate. The starting 2,5-dimethoxyanilides were prepared by chemoselective acylation of 2,5dimethoxyaniline with a series of b-oxo thioesters obtained by regioselective alkylation of S-tert-butyl acetothioacetate (1) at C 2 and/or C 4 . The introduction of electrophiles other than alkyl groups at C 2 on 1 was also studied.Quinoline-2,5,8(1H)-triones have been employed by our group 1 as precursors to antitumor 1,8-diazaanthracene-2,9,10-triones, designed as analogs of the natural thymidilate synthase inhibitor diazaquinomycin A. 2 The methods currently available for the preparation of these quinones are restricted to 3-substituted 3 or to 4-methyl derivatives, 4 and this limits the range of structural variations that can be introduced in the 1,8-diazaanthracene system. We envisaged that the acid-promoted cyclization of b-oxo anilides (i.e., the Knorr quinoline synthesis 5 ) might serve as the key step of a more general route. However, and in spite of the long tradition of this reaction, there are very few examples of its application to the preparation of 3,4-disubstituted quinoline systems, 6 probably because of difficulties in the synthesis of the anilide precursors.

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“…4 The application of high oxidation state lead 5,6 and bismuth 7 for carboncarbon bond formation for a variety of reacting partners has also been developed. These reactions proceed via a catalytic cycle involving a sequence of oxidative addition/reductive elimination processes at palladium.…”

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confidence: 99%