Unusual Product from Condensative Cyclization: Pyrano[3,2-f]quinolin-3,10-diones from 6-Amino-5-[(trimethylsilyl)ethynyl]-2H-chromen-2-one and Aryl Aldehydes

A new efficient and simple route for the synthesis of 8,9-dihydro-3H-pyrano[3,2-f]quinoline-3,10(7H)-dione derivatives has been accomplished via sulfuric acid promoted condensation-­cyclization of 6-amino-5-[(trimethylsilyl)ethynyl]-2H-chromen-2-one and aromatic aldehydes. The products can be oxidized to the corresponding 10-methoxy-8-aryl-3H-pyrano[3,2-f]quinolin-3-one derivatives by FeCl3˙6H2O in methanol.