Study of the ortho-methoxy substituent group effect in selective demethylation reactions of methoxybenzoic acids.

The methylation of the hydroxyl group is largely used in synthesis due to high stability of the methoxy group to several reaction conditions. However, the procedures for O-demethylation of aryl methyl ethers involves the use of costly reagents or elaborated methods, requiring anhydrous conditions or difficult to carry out. In most cases the simplest methods of Odemethylation are not selective, resulting in complete demethylation products1,2. In order to prepare demethylated 3,5-dimethoxybenzoic derivatives, this work presents a new selective methodology for demethylation of phenolic methoxyl group using simple and inexpensive reagents. The methodology was adjusted to 3,5-dimethoxybenzoic acid and is summarized in the reaction of aryl methyl ether with ethylene glycol, KOH, at 120 °C or 180 °C.