p-Sulfonic Acid Calix[4]arene as an Efficient Catalyst for One-Pot Synthesis of Pharmaceutically Significant Coumarin Derivatives under Solvent-Free Condition

Table 2

Optimization of the reaction medium for the synthesis of 4-methyl-2H-chromen-2-one ().

Entry	Catalyst (mg)	Solvent	Temp. (°C)	Time (h)	Yield (%)
1	25	THF	80	5	60
2	25	CH3CN	80	5	67
3	25	CH2Cl2	80	12	30
4	25	n-Hexane	80	12	20
5	25	Solvent-free	80	3	78
6	15	Solvent-free	80	5	50
7	25	Solvent-free	80	3	78
8	45	Solvent-free	80	3	88
9	60	Solvent-free	80	2.5	90
10	45	Solvent-free	r.t	24	30
11	45	Solvent-free	50	10	60
12	45	Solvent-free	80	3	88
13	45	Solvent-free	90	2.5	95
14	45	Solvent-free	120	2.5	96

Reaction condition: resorcinol (1 mmol) with Ethyl acetoacetate (1 mmol), p-sulfonic acid calix[]arene.
Isolated yield.