Synthesis of benzofuro[3,2‐b] quinolin‐6(11H) one and derivatives

A new and efficient synthesis of benzof'uro[3,2‐b]quinolin‐6(11H) one (3) is reported, by treatment of 2‐ {[(phenoxy)acetyl]amino} benzoic acid (6a) with polyphosphoric acid. An intermediate in the conversion of 3 to 6a, namely, 2‐(3‐benzofuranylamino)benzoic acid (7), was defined. An improved method for the synthesis of 6a is also described, which was used to prepare analogs (6b‐n) of 6a. In addition, an 11‐alkoxy derivative (8) and 11‐dialkylamino derivatives (10 and 11) of benzofuro [3,2‐b]quinoline were prepared from 3.