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 K₃[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 K₃[Fe(CN)₆] to 2.

Keywords:

• 4‐Aryldihydroisoquinolines
• 4‐arylisoquinolin‐1‐ones
• 4‐arylisoquinolines
• disproportionation
• isoquinolines
• isoquinolinium perchlorates
• isoquinolinones
• oxidation with Fe(III)
• oxidative cyclization

Acknowledgment

Uludağ University Research Fund is gratefully acknowledged for its financial support (Project No 2001‐2).