HY zeolite catalyzes the ortho–methylation of 1–naphthol

The selective ortho–alkylation of 1–naphthol with methanol is carried out over various commercially available acid solid catalysts under relatively mild reaction conditions (<300 ºC), in batch, and anhydrous zeolite HY shows the best catalytic activity. Removal of the strongly adsorbed water in the zeolite is key for the alkylation reaction. Mechanistic studies based on isotopically labelled experiments reveal the transformation of O–methylated 1–naphthol into the desired ortho–C–methylation product after intramolecular rearrangement of the methyl group. These results open the way to design a new synthesis of ortho–methyl 1–naphthol and, consequently, of vitamin K3, based on a commercially available, inexpensive and non–toxic solid catalyst such as HY zeolite.