Synthesis of Furo[2,3‐c]isoquinoline Derivatives

Abstract 2‐Methylfuro [2,3‐c] isoquinolin‐5(4H)one (X) and 1‐phenylfuro[2,3‐c] isoquinolin‐5(4H)one (XI) were prepared from thermal cyelization via the Curtius rearrangement of 5‐methyl‐3‐phenyl‐2‐furoyl azide (VI) and 3,4‐diphenyl‐2‐furoyl azide (VII), respectively. Stability against acid, alkylation and conversion of the NHCO group to a C=N double bond of X and XI, which were synthesized, are described. Also, 5‐substituted furo[2,3‐c] isoquinolines (XVIIIa‐c) and (XIXa‐c) were prepared.