Sulfamic Acid Catalyzed Atom Economic, Eco-friendly Synthesis of Novel 7-(Aryl)-10-thioxo-7,9,10,11-tetrahedro-6H-pyrimido-[54:5,6]pyrano[3,2-c]quinoline-6,8(5H)-dione and its Derivatives

A series of novel 7-(3-chloro-phenyl)-10-thioxo-7,9,10,11-tetrahedro-6H-pyrimido-[54:5,6] pyrano[3,2-c]quinoline-6,8(5H)-dione derivatives have been synthesized through the multi-component condensation of aromatic aldehydes, barbituric acid, and 2,4-dihydroxy quinoline, using heterogeneous sulfamic acid catalyst in water-ethanol (4:1) solvent system under reflux condition. The present protocol is endowed with charming description such as green synthetic procedure, short reaction time, easy work-up procedure, and excellent yield and high atom economy of pyranoquinoline derivatives. In this study, sulfamic acid is used as a heterogeneous catalyst that is easily recoverable and recyclable. The proposed multi-component reaction has been studied with detail mechanism and spectroscopic data. This is one of the potential greener synthetic approaches to build up the series of pyranoquinoline heterocycles.