☆ 4.5 Article

Synthesis and Characterization of Novel Quinone Methides: Reference Electrophiles for the Construction of Nucleophilicity Scales

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY (2009)

Journal

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY

Volume 2009, Issue 19, Pages 3203-3211

Publisher

WILEY-V C H VERLAG GMBH

DOI: 10.1002/ejoc.200900299

Keywords

Electrophilicity; Nucleophilicity; Kinetics; Linear free-energy relationships; Quinone methides

Categories

Chemistry, Organic

Funding

Deutsche Forschungsgerneinschaft (DFG) [SFB 749]

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Abstract

Novel synthetic routes to the aryl-substituted quinone methides 3a-f have been developed, and a previously reported Mannich approach has been used for the syntheses of the acceptor substituted quinone methides 2e-g. The second-order rate constants for the reactions of R4 and 2e-g with the carbanions 9a-h were determined photometrically in DMSO. With Equation (1), log k(2) = s (N + E), and the known nucleophilicity parameters N and s for the carbanions 9a-h, it was possible to calculate the electrophilicity parameters E for these quinone methides. With E parameters between -12 and -17, these readily accessible quinone methides are recommended as reference electrophiles for the construction of nucleophilicity scales. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

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