Studies on 1, 2, 3, 4-Tetrahydroisoquinolines. II. A One-pot Synthesis of 1-Arylmethyl-1, 2, 3, 4-tetrahydroisoquinolines from an Isoquinolinium Salt

In connection with our previous study on the β-adrenoceptor activities of the positional isomers of trimetoquinol, various 1-arylmethyl-1, 2, 3, 4-tetrahydroisoquinolines (10b-i) were synthesized. The Barbier reaction of the quaternary salt (7) with arylmethyl halides, followed by sodium monoacetoxyborohydride [NaBH3 (OAc)] reduction in a one-pot procedure, gave the tribenzyltetrahydroisoquinolines (9b-i) in excellent yields. Catalytic debenzylation of 9b-i furnished 10b-i. None of the compounds (10b-i) exhibited significant bronchodilating activity.