Enantioselective synthesis of spiro[indoline-3,1′-pyrazolo[1,2-b]phthalazine] derivatives via an organocatalytic three-component cascade reaction

Abstract

An asymmetric synthesis of spiro[indoline-3,1′-pyrazolo[1,2-b]phthalazine] derivatives was first developed through an organocatalysed cascade Knoevenagel/Michael/cyclization reaction using a quinidine-derived squaramide. Under the optimized conditions, the three-component reaction of isatins, malononitrile (cyanoacetate) and phthalhydrazide yields the desired pyrazolophthalazinyl spirooxindoles in good yields (73–90%) with up to >99% enantiomer excess (ee).