An environmentally benign and atom-economical process to construct a unique quinoline-based tetracyclic scaffold, through sequential hydration-condensation-double cyclization reactions, has been described. The reaction starts with readily available pyridine-substituted o-alkynylanilines and β-keto esters, promoted by p-toluenesulfonic acid in ethanol in one pot. In the absence of β-keto esters, multisubstituted quinolines are formed bimolecularly in reasonable yields.