Photochemical synthesis of 1,2,3,4-tetrahydroisoquinolin-3-ones from N-chloroacetylbenzylamines

When N-chloroacetyl-3-hydroxybenzylamine (37) in aqueous acetonitrile was irradiated, both ortho and para photocyclizations with reference to the OH group occurred to give 7- and 5-hydroxy-3-oxo-1,2,3,4-tetrahydroisoquinolines (52,53). Similarly, 1-methylisoquinoline derivatives (54,55) were synthesized. N-Chloroacetyl-3,5-dihydroxybenzylamine (39) gave a single photoproduct, 5,7-dihydroxy-3-oxo-1,2,3,4-tetrahydroisoquinoline (56). These photocyclizations were smoothly extended to the synthesis of 1-benzyl, 1-(4′-methoxybenzyl)- and 1-(3′,4′,5′-trimethoxybenzyl)-isoquinoline derivatives (58～64).