The preparation of benzyl esters using stoichiometric niobium (V) chloride versus niobium grafted SiO₂ catalyst: A...

Two solvent free methods of a one-to-one alcohol/acid mol ratio synthesis of benzyl esters of the formic, acetic, benzoic, salicylic, nicotinic, and oxalic acids are described. The stoichiometric reactions used 1.5 mol ratio solid NbCl₅ as the reagent and required from two to three hours for completion at room temperature; for the catalytic processes, NbCl₅ was grafted directly, at room temperature, onto a silica gel of specific area of 507 m²g^-1, produced from construction sand and sodium carbonate, forming a 5.4% Nb w/w SiO₂-Nb gel with a specific area of 412 m²g^-1. At 10% w/w catalyst/alcohol ratio, this SiO₂-Nb catalyst gave similarly very good yields but required from 6 to 9 hours at the reflux temperature of the slurry. The catalyst could be re-used three times.