As a new extension of the Mannich reaction of naphthols, 1-(hydroxynaphthyl)-substituted 1, 2, 3, 4-tetrahydroisoquinolines were synthesized by the nucleophilic addition of 1-or 2- naphthol to 3, 4-dihydroisoquinolines under solvent-free conditions, using microwave irradiation. The additions to 3-methyl-6, 7-dimethoxy-3, 4-dihydroisoquinoline proved to be a highly diastereoselective processes, resulting in the cis isomers as the main or the only ...