Aerobic selective oxidation of (hetero)aromatic primary alcohols to aldehydes or carboxylic acids over carbon supported platinum

Abstract

The synthesis of substituted benzaldehydes, benzoic acids, heterocyclic aromatic aldehydes and acids has been studied via the oxidation of the aromatic alcohols with air under mild pressure (<20bar) at 100°C, in the presence of a 1.95wt.% Pt/C catalyst. The solvent was found to play the most important role in determining the selectivity of the oxidation products. Changing the solvent enabled tuning the reaction either to the aldehyde (pure dioxane), or the carboxylic acid (dioxane/aqueous solution without or with addition of sodium hydroxide). This oxidation method allowed to effectively oxidize many substituted benzylalcohols with various electron-releasing or -attracting groups (NO2, Me, OMe, Cl, Br, OH, phenyl, …) and heterocyclic alcohols including nitrogen and sulphur atoms (2-thiophenemethanol, 2- and 4-pyridine methanol compounds).