Iron salicylate catalyzes oxidative esterification of biomass-derived aldehydes

The production of specialty chemicals from lignocellulosic biomass can be increased by valuing underutilized biomass products using sustainable methods. The present work reports the activity of the biomass-derived iron(III) salicylate as a biocompatible and recyclable catalyst for the oxidative esterification of multi-functional aldehydes obtained as products from biomass processing. Esters were obtained in the presence of methyl, ethyl, i -propyl, and amyl alcohols as solvents, at room temperature and with H 2 O 2 as a green oxidant. The catalytic system is selective for the esterification of 2- and 4-hydroxybenzaldehydes, namely salicylaldehyde, o -vanillin and vanillin; as well as of furfural and benzaldehyde, while esters of 9-formylanthracene and ( E )-cinnamaldehyde were obtained concomitantly with products of hydroxylation of the polyaromatic ring to ethyl 10-hydroxyanthracene-9-carboxylate (η 46%), and of double bond oxidative cleavage of cinnamaldehyde to ethyl benzoate (η 27%), respectively. The ester products have applications as fragrances, flavors, photo- or bioactive compounds, or as intermediates for synthesis. The results were benchmarked against other Fe(III)–based catalysts, such as Fe(III) porphyrins ([Fe(TSPP)Cl] and [Fe(TMPyP)Cl]) and iron oxide nanoparticles. These studies confirmed the higher performance of Fe(III) salicylate. Graphical Abstract