Substitution reactions of para-hydroxybenzyl alcohols are catalyzed by the phosphazene base t-Bu-P2. This system is compatible with substrates bearing various functionalities, including alkyl, methoxy, thiophenyl, halogen, and ester moieties. Mechanistically, the reaction proceeds via E1cB elimination of the benzylic hydroxyl group from the phenoxide intermediate to generate a para-quinone methide, followed by nucleophilic 1,6-addition.

Abstract

Herein, we report the substitution reactions of para-hydroxybenzyl alcohols catalyzed by the phosphazene base t-Bu-P2. This system is compatible with substrates bearing various functionalities, including alkyl, methoxy, thiophenyl, halogen, ester, and amide moieties. Thiols, 1,3-dicarbonyl compounds, and amines can be used as nucleophiles. Mechanistically, the reaction proceeds via E1cB elimination of the benzylic hydroxyl group from the phenoxide intermediate to generate a para-quinone methide intermediate, followed by nucleophilic 1,6-addition.