Oxidative Functionalization of Catechol Derivatives Substituted with Electron-Withdrawing Groups.

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,ß-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.

Oxidative two-way regiocontrolled coupling of 3-methoxycarbonylcatechol and indoles to arylindoles.

3-Methoxycarbonylcatechol effectively underwent two-way regiocontrolled coupling with indoles via an ortho-benzoquinone intermediate, resulting from phenyliodine(III) diacetate oxidation, to generate 4-adducts or 5-adducts with or without BF3·Et2O in a one-pot manner. DFT calculations confirmed the obtained regioselectivities.