ENVIRONMENTALLY FRIENDLY AND HIGHLY EFFICIENT Co(OAc)_2-CATALYZED AEROBIC OXIDATION TO ACCESS 2,6-DI-ELECTRON-DONATING GROUP SUBSTITUTED 4-HYDROXYBENZALDEHYDES

摘要

A highly efficient and green aerobic oxidation has been developed for selectively preparing a series of valuable 2,6-dialkyl-, dialkoxyl-, and alkoxylalkyl-substituted 4-hydroxybenzaldehydes from corresponding 4-cresols in good to excellent yields, using a catalytic system of Co(OAc)_2 ?4H_2O (1.0 mol%)-NaOH (1.0 equiv)-O_2 (1.0 atm) in aqueous ethylene glycol (EG/H_2O=20/1, v/v) at 50 ℃. Furthermore, a plausible mechanism was proposed for the direct oxyfunctionalization of the aromatic methyl group into the aldehyde group.