Reactivity of Quinone Methides

MODELING PROPERTIES AND REACTIVITY OF QUINONE METHIDES BY DFT CALCULATIONS... 

Bolton, J. L. Valerio, L. G. Thompson, J. A. The enzymatic formation and chemical reactivity of quinone methides correlate with alkylphenol-induced toxicity in rat hepato-cytes. Chem. Res. Toxicol. 1992, 5, 816-822. 

This chapter will focus on o- and p-quinone methides and will be divided into two parts. The first will present methods for generating quinone methides in photochemical and solvolysis reactions and will emphasize how the structure and stability of quinone methides dictates the pathways for their formation. The second section will discuss the results of experiments to characterize the reactivity of quinone methides with nucleophilic reagents, and the broader implications of these results. The scope of this presentation will reflect our interests, and will focus on studies carried out at Buffalo. We considered briefly writing a comprehensive chapter on quinone methides, but abandoned this idea when we learned of Steven Rokita s plans to edit a 12-chapter text, which presents an extremely comprehensive coverage of the chemistry and biochemistry of quinone methides.9... 

Several general synthetic methods have been developed that utilize the novel reactivity of quinone methides generated by oxidation of phenol precursors. Angle and Ranier have generated 2,6-dialkyl or 2,6-dialkoxy-substituted / -quinone methides 51 by oxidation of the corresponding phenols with Ag20. 

During my early years as an assistant professor at the University of Kentucky, I demonstrated the synthesis of a simple quinone methide as the product of the nucleophilic aromatic substitution reaction of water at a highly destabilized 4-methoxybenzyl carbocation. I was struck by the notion that the distinctive chemical reactivity of quinone methides is related to the striking combination of neutral nonaromatic and zwitterionic aromatic valence bond resonance structures that contribute to their hybrid resonance structures. This served as the starting point for the interpretation of the results of our studies on nucleophile addition to quinone methides. At the same time, many other talented chemists have worked to develop methods for the generation of quinone methides and applications for these compounds in organic syntheses and chemical biology. The chapter coauthored with Maria Toteva presents an overview of this work. 

PospfSil J, NeSpurek S and Zweifel H (1996) The role of quinone methides in thermostabilization of hydrocarbon polymers, Part I, Formation and reactivity of quinone methides, Polym Degrad Stab 54 ... 

Elder, T. J., M. L. McKee, and S. D. Worley. 1988. The application of molecular orbital calculations to wood chemistry. V. The formation and reactivity of quinone methide intermediates. Holzforschung 42(4) 233-240. 

The formation of the isomers of the quinonemethide (131) by irradiation of the corresponding o-hydroxybenzyl alcohol has been described. A further study on the formation and reactivity of quinone methides has reported the flash photolysis of the phenol derivative (132) in perchloric acid solution. This affords the p-quinone methide (133). Irradiation of the benzene derivative (134) results in the formation of the quinodimethane (135). A two-colour laser method... 

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