Hydroxyl-directed Diels-Alder reaction

Beginning the approach, enone 38 underwent a Luche reduction to give the allyl alcohol 37 (Scheme 8). According to the published conditions, the hydroxyl-directed Diels-Alder reaction was carried out with methyl acrylate. 

We characterized and further studied this basic mechanism of covalent affinity labeling using spectroelectrochemical techniques. The kinetics and stability of quinone oxidation products at high dilution and low pH were consistent with the proposed mechanism, as was the concentration dependence of rapid labeling reactions of the more reactive catechol with the receptor.1215 Spectroelectrochemical and direct cyclic voltametric determination of the half-potentials of the hydroxylated quinones were further consistent with their intermediacy in the labeling reactions of TMC.15 The quinone oxidation products of 4- and 5-HTMC were characterized in part as cyclopentadiene Diels-Alder adducts.15 The instantaneous reactions of these hydroxy TMCs with receptor were consistent with their intermediacy in the TMC reactions. From the concentration dependence of the half-of-sites labeling reactions we could deduce Kd for each isomer fC,(4-HTMC) = 224 98 pM, K/5-HTMC) = 39 17 juM. 

Other applications of Evans oxazolidinones include alkylation, Diels-Alder cycloaddition, Michael addition, and electrophilic halogenation, hydroxylation, and amination reactions [15]. In all cases, the conformational rigidity of the reaction TS allows the substituents at the stereocenters to direct efficiently the reaction course. 

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