A Simple, Efficient and Environmentally Benign Synthetic Protocol for the Synthesis of Spirooxindoles Using Choline Chloride-Oxalic Acid Eutectic Mixture as Catalyst/Solvent System

An efficient and environmentally benign domino protocol has been presented for the synthesis of structurally diverse spirooxindoles spiroannulated with pyranopyridopyrimidines, indenopyridopyrimidines, and chromenopyridopyrimidines involving three-component reaction of aminouracils, isatins and cyclic carbonyl compounds in deep eutectic solvent (choline chloride-oxalic acid: 1:1) which acts as efficient catalyst and environmentally benign reaction medium. The present protocol offers several advantages such as operational simplicity with easy workup, shorter reaction times excellent yields with superior atom economy and environmentally benign reaction conditions with the use of costeffective, recyclable, non-toxic and bio-degradable DES as catalyst/solvent.