One pot synthesis of new benzopyranopyridines via Friedlander condensation

An ecofriendly synthetic route has been developed for the synthesis of novel benzopyrano [2,3-b] pyridine derivatives (3a-j) in excellent yield via Friedlander condensation, employing 2-amino-3-formyl-chromone (1a-b) and cyclic active methylene compounds (2a-e) in the presence of non toxic, green Zn(l-proline)2 Lewis acid catalyst in water. The catalyst is recyclable and shows activity up to three cycles.