A derivatization-directed three-component synthesis of fluorescent spiro [dihydropyridine-4,3ʹ-indoline]s

The synthesis of spiro[chromeno[4,3-b]pyrazolo[4,3-e]pyridine-7,3ʹ-indoline]s is achieved via three-component reactions of 5-amino-3-methylpyrazole, 4-aminocoumarin, and isatin derivatives. This protocol provides expedient synthesis of 10-unsubstituted derivatives of the parent heterocyclic spiro framework and does not lead to coumarin ring opening. The synthesis is highly convergent as no by-products are present in the reaction mixtures. The spiro products show violet fluorescence emissions depending on the nature of their substituents.