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

Novel synthetic routes to the aryl‐substituted quinonemethides 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 3c – f 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.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)