The Oxidative Coupling of Methyl Benzoate

The Oxidative Coupling of Methyl Benzoate

The reaction of methyl benzoate (MBA) with pressurized (50 atm) artificial air (50 mol% O2–N2 mixture) at 150–200°C over a soluble palladium catalyst [PdLL2′] (L=phen, bipy, dppe; L′=OAc, TFA) afforded isomeric dimethyl bibenzoic acid esters (DMBBA). Different factors affect the reactivity and regio...

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Bibliographic Details
Published in:Journal of catalysis Vol. 193; no. 1; pp. 49 - 57
Main Authors: Iretskii, A.V., Sherman, S.C., White, M.G., Kenvin, J.C., Schiraldi, D.A.
Format: Journal Article
Language:English
Published: Amsterdam Elsevier Inc 01-07-2000
Elsevier
Subjects:
1,10-phenanthroline
Catalysis
Catalytic reactions
Chemistry
C–H activation
Exact sciences and technology
General and physical chemistry
methyl benzoate
oxidative coupling
palladium
Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
triflic acid
trifluoromethanesulfonic acid
oxidative coupling
methyl benzoate
C–H activation
triflic acid
palladium
1,10-phenanthroline
trifluoromethanesulfonic acid
Ester
Catalytic reaction
Regioselectivity
Palladium Complexes
Homogeneous catalysis
Benzenic compound
Platinoid Complexes
Oxidation
Transition metal Complexes
Catalyst
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Summary:The reaction of methyl benzoate (MBA) with pressurized (50 atm) artificial air (50 mol% O2–N2 mixture) at 150–200°C over a soluble palladium catalyst [PdLL2′] (L=phen, bipy, dppe; L′=OAc, TFA) afforded isomeric dimethyl bibenzoic acid esters (DMBBA). Different factors affect the reactivity and regioselectivity of the process. The reactivity is enhanced by trifluoromethanesulfonic acid, arguably by activating the C–H bond of the aromatic ring by its protonation. The increase of temperature not only increases the reaction rate (EA=5.5 kcal/mol) but also favors a formation of an ortho-coupled product. Ligands with strong trans influence (L=phen, bipy, or dppe) direct the oxidative coupling away from 2,X′-isomers (X=2, 3, or 4). Overall, electronic properties of a palladium catalyst are more important than steric restriction of the same catalyst for altering the activity and regioselectivity for MBA coupling.
ISSN:0021-9517
1090-2694
DOI:10.1006/jcat.2000.2865