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).
Song et al. (2026) studied this question.