Catechols possessing electron-withdrawing groups at the C3 position effectively underwent oxidative functionalization at the C4 position in the presence of phenyliodine(III) diacetate (PIDA) and heteroarene nucleophiles (e.g., indole, indazole, and benzotriazole) to produce the corresponding biaryl products. The PIDA-mediated oxidation of catechol derivatives afforded the ortho-benzoquinone intermediate, which subsequently underwent regioselective nucleophilic addition to the α,β-unsaturated carbonyl moiety of ortho-benzoquinone using indole, indazole, and benzotriazole to give 4-substituted catechol derivatives in a one-pot manner. Notably, the nucleophilic substitution positions of indazole and benzotriazole were perfectly controlled. Additionally, the reaction using N-methylaniline as the nucleophile afforded a tertiary amine product.
Keywords: catechol; heterocycle; oxidative functionalization.