Water as catalyst and solvent: Tetrahydropyranylation of alcohols in an aqueous medium

Abstract

Water is found to catalyze the tetrahydropyranylation of alcohols at elevated temperature. Interestingly, tetrahydropyranylation of alcohols works under a wide range of pH, 6.5 to 2, and does not work beyond pH 7.5 in an aqueous medium. Hydrophobic interactions between the substrate alcohol and dihydropyran ether (DHP) and favorable pKa's of water, alcohols, and protonated hydroxyl and protonated ethereal functions are the driving forces for the reaction. Thus the reaction, which is carried out in anhydrous aprotic solvents, can be carried out in aqueous medium in an environmentally benign way. © ARKAT.