Rapid four-component synthesis of dihydropyrano[2,3-c]pyrazoles using nano-eggshell/Ti(IV) as a highly compatible natural based catalyst

Table 3 Catalytic performances of NEST in comparison with some other catalysts for synthesis of 5a

Entry	Catalyst	Solvent	Temp (°C)	Time (min)	Yield^a (%) [Refs.]
1	I₂	H₂O	r.t	10	90 [49]
2	Isonicotinic acid	–	80	10	92 [50]
3	Piperidine	H₂O	r.t	5–10	89 [51]
4	γ-Alumina	H₂O	Reflux	35	90 [20]
5	Et₃N	EtOH	Reflux	15	72 [26]
6	NEST^b	–	r.t	10	92

ISSN: 2661-801X