Ferric Nitrate as a Bifunctional Catalyst for Dehydration and Oxidative Cleavage-Esterification of Tertiary Alcohols.

Abstract

The selective oxidative cleavage and functionalization of C(OH)-C bonds in tertiary alcohols harbor immense feasibility in organic synthesis and enable the production of high value-added chemicals from renewable biomass. However, it remains a challenge, owing to the inherent kinetic inertness and thermodynamic stability of C(OH)-C bonds and the lack of C_α-H. Taking the huge potential and challenge of C(OH)-C bond activation and functionalization into consideration, herein, we show the first example of an inexpensive bifunctional ferric nitrate catalyst for catalytic direct oxidation of structurally distinct tertiary alcohols to esters with environmentally benign molecular oxygen as an oxidant and MeOH as a solvent, without the assistance of any additives. Detailed mechanistic studies reveal that this tandem catalytic oxidative process is initiated by the synergistic effects of an iron ion and nitrate ion, which serve as Lewis acids for dehydrating and a nitrogen dioxide radical precursor for inducing an oxidative cleavage, respectively.