Table 3.

Evaluation of catalytic activity of NH₄Cl in the synthesis of 5a

Entry	Amount of NH4Cl (mol%)	Yielda (%)
1	5	80
2	10	92
3	15	92
4	20	89
5	25	85

The reaction was carried out with ethyl 2′-amino-3′-cyano-1-((diphenylamino)methyl)-6′-methyl-2-oxospiro[indoline-3,4′-pyran]-5′-carboxylate (3a) (10 mmol) and 2-hydroxybenzaldehydes (4a) (10 mmol), and NH₄Cl in 10 mL ethanol at refluxing temperature/2 h

^aIsolated yield of (5a)