Asymmetric Synthesis of Spiro [indoline‐3,1′‐pyrazolo[1,2‐ a ] pyridazine] Derivatives via Organocatalytic One‐Pot Domino Reaction

Asymmetric synthesis of spiro [indoline‐3,1′‐pyrazolo[1,2‐ a ] pyridazine] derivatives was first developed through an organocatalysed domino Knoevenagel/Michael/cyclization reaction using a quinine‐derived squaramide. Under the optimized conditions, the three‐component reaction of isatins, the active methylene compounds and maleic hydrazide yields the new type of spiro‐heterocycle compounds in middle yields (55%–70%) with up to 98% enantiomer excess (ee).