Novel methods for the synthesis of 4-arylisoquinolinium perchlorates and 4-arylisoquinolin-1-ones

Abstract

2-Benzylamino-1-phenyl-ethanones 1 were converted to the corresponding isoquinolinium perchlorates 2 in high yields using 70% HClO4-FeCl3 mixture as a cyclization and oxidation reagent. A mild and high yielding method for the oxidation of perchlorates 2 to isoquinolin-1-ones 3 involving the treatment of 2 with KOH and K-3[Fe(CN)(6)] in THF-H2O two-phase system at room temperature was developed. Compounds 2a-g were shown to be disproportionate to 3 and the corresponding 1,2-dihydroisoquinoline 4 in the presence of base, which in turn is oxidized by K-3[Fe(CN)(6)] to 2.