Regioselective Monomethylation of Unsymmetrical Naphthalenediols With Methanolic HCl

Abstract

Treatment of naphthalene-1,3-diol and naphthalene-1,7-diol with methanol containing dry hydrogen chloride at room temperature gives exclusively 3-methoxy-1-naphthol and 7-methoxy- 1-naphthol, respectively. Of the other two unsymmetrical naphthalenediols, the 1,2-isomer was unreactive and the 1,6-isomer gave a mixture of regioisomers under the same conditions. Two symmetrical diols (the 1,5- and 2,7-isomers) examined by the same procedure gave the monomethyl ethers in 60-70% yields.