Green Oxidations of Aldehydes to Carboxylic Acids and Esters

Oxidation reactions are fundamental and useful chemical transformations, especially for industries. However, the use of heavy metals or stoichiometric organic agents as common oxidants are nowadays rejected, preferring greener and economical procedures. Here, we propose a simple and sustainable method to oxidize aldehydes at room temperature using, in water, hydrogen peroxide as oxidant and PhSe)₂ as catalyst which is a not expensive and commercially available organoselenium reagent. Differently substituted aromatic and aliphatic aldehydes underwent the oxidation in good yields. In the presence of an alcoholic medium, the same substrates can be directly converted into the corresponding esters using the same reaction conditions. In order to avoid the side formation of carboxylic acid the reactions were heated at 50°C in acidic conditions. We also demonstrated that in the same conditions carboxylic acid was not transformed into the corresponding ester. This latter evidences suggest that the oxidation occurred on the hydrated aldehydes or on the hemiacetal in the presence of water and alcohols respectively . Aknowledgment: Technical support of Mr. Lorenzo Bettona from I.T.T.S. "Alessandro Volta", Perugia has been particularly appreciated.