An efficient ultrasound promoted catalyst-free protocol for the synthesis of chromeno[4,3-b]quinolin-6-ones

A convenient, catalyst-free protocol for the quantitative synthesis of fused chromeno[4,3-b]quinolin-6-ones has been developed by simple one-pot reaction of substituted anilines with 4-chloro-3-formylcoumarin using ultrasound irradiation. The protocol offers the advantages of mild reaction conditions, short reaction times and high yields. Graphical Abstract Tetracyclic chromeno-quinolines are precipitated as pure products from the reaction of 4-chloro-3-formyl-coumarin and aromatic anilines in ethanol under ultrasound irradiation.