Convenient one-step synthesis of a medicinally relevant benzopyranopyridine system

Benzopyrano[2,3-b]pyridine is an important privileged medicinal scaffold. A three-component reaction of salicylalde-hydes, thiols and 2 equiv of malononitrile that leads to the formation of a series of compounds incorporating 2,4-diamino-3cyano-5-sulfanylbenzopyrano[2,3-b]pyridine framework is described. A proposed mechanism with the supporting experimental data is presented. (c) 2006 Elsevier Ltd. All rights reserved.