Deep eutectic solvent promoted efficient and environmentally benign four-component domino protocol for synthesis of spirooxindoles

Abstract

An efficient and environmentally benign one-pot four-component domino protocol has been presented for the synthesis of structurally diverse spirooxindoles spiroannulated with pyrazolopyrimidophthalazines, indenopyrazolophthalazines, chromenopyrazolophthalazines and indazolophthalazines involving the reaction of phthalic anhydride, hydrazine hydrate, isatins and cyclic diketones/diamides in a deep eutectic solvent (choline chloride : urea: 1 : 2). The present protocol offers some advantages such as operational simplicity with easy workup, shorter reaction times, good to excellent yields with superior atom economy and environmentally benign reaction conditions.