The alkaline hydrolysis of 4-methoxycoumarin

Abstract

The aqueous alkaline hydrolysis of 4-methoxycoumarin occurs in two stages. In the first, the lactone ring is opened at a rate directly proportional to the concentration of base. In the second, the methoxy group is replaced by an unusual route that depends upon the presence of an un ionised phenolic hydroxy group and is therefore inversely proportional to the concentration of base. Methanolysis by methoxide ion in methanol occurs primarily at position 4 and replaces the methoxy group before the ring is opened; the difference from the aqueous hydrolysis is ascribed to solvent effects.