Table 2. Comparative Study of the Efficiency of Present Catalyst and Other Reported Catalysts for A2 Synthesis.

sl. no.	catalyst	conditions	time (min)	yield (%)	derivative	catalyst recycle-ability	ref
1	NH4OAc (2 mmol)	H2O, reflux	57–81	80–90	17		(38)
2	sulfonated rice husk (60 mg)	solvent-free, 60–80 °C	60	90–98	17	7	(39)
4	nanosized MgO [65 mol %]	EtOH, reflux	18–29	88–91	6		(40)
5	n-Fe3O4@TDI@TiO2 [0.028 g]	solvent-free, 70 °C	14–40	82–95	22	6	(41)
6	citric acid/MCM-48 [50 mg]	EtOH, RT	15	92–98	11	7	(42)
7	K2CO3 [5 mol %]	H2O, ultrasound	12–15	85–92	7		(43)
8	[H2-DABCO][HSO4]2 (30 mg)	EtOH, stirring, room temperature	5–15	76–99	28	5	present work