On In Situ Prepared Cu–Phenanthroline Complexes in Aqueous Alkaline Solutions and Their Use in the Catalytic Oxidation of Veratryl Alcohol

Abstract

The in situ prepared complex based on copper(II) sulfate and 1,10-phenanthroline (phen) and its performance in the catalytic oxidation of veratryl alcohol (3,4-dimethoxybenzyl alcohol) to veratraldehyde with O 2 in alkaline aqueous solutions have been studied. In aqueous solution, the structure of Cu-phen complexes varies with reaction conditions; by changing either the copper-to-ligand molar ratio or the pH, the amount of coordinated 1,10-phenanthroline and hydroxido ligands in the coordination sphere of copper can be altered in a controlled manner. The highest activities are achieved in the pH range 12.6-13.3, which correlates with the presence of the [Cu(phen)(OH) 2 ] species according to

An Overview of Selective Oxidation of Alcohols: Catalysts, Oxidants and Reaction Mechanisms

“…Ahmad et al [54] devoted themselves into developing green catalytic systems for alcohol oxidation [3,[55][56][57][58][59][60]. They reported detailed studies on oxidation of benzylic alcohols in water over several copper salts catalysts with H 2 O 2 as an end oxidant.…”

Pulp delignification with oxygen and copper(II)-polyimine complexes

“…All the ligands are commercially available and were supplied by Aldrich (Lyon, France). The Cu-ligand complex was preformed in distilled water by adding 22.1 mg Cu(II) as sulfate (CuSO 4 , 98% purity, provided by Aldrich), and the Cu/ligand ratio was 1:2 (see Korpi et al 2007).…”

“…The mechanism of Cu-polyimine complexes in this context is not well understood, although they are known to catalyze the oxidation of alcohol to carbonyl groups. For example, veratryl alcohol gives veratryl aldehyde in high yield when submitted to oxygen treatment with Cu(II)-phenanthroline under alkaline conditions (Korpi et al 2007). Lignin contains alcohol groups in α-position of the phenolic rings, similar to veratryl alcohol.…”

“…Copper-polyimine complexes, such as Cu(II)-phenanthroline and Cu(II)-bipyridine complexes (Germer 1991(Germer , 1995a(Germer , 1998(Germer , 1999Korpi et al 2004Korpi et al , 2006Korpi et al , 2007Sippola and Krause 2005), received special attention. They are simple to prepare and stable in the alkaline delignification medium and catalyze efficiently the oxidation of nonphenolic lignin model compounds by oxygen.…”

Magnesium Oxide‐catalyzed Oxidative Depolymerization of EFB Lignin

“…As oxygen is inexpensive, nontoxic, and abundant, the development of an oxidative depolymerization process, especially one that employs oxygen in the form of air, would be an attractive solution for oxidative lignin depolymerization. It has been reported that the oxidative depolymerization of lignin using oxygen has been effectively carried out in homogeneous solutions assisted by enzymes, organometals, acids, and alkaline catalysts …”