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Table 1 Preparation of 5 h in the presence of NEST under various conditions

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

Entry Conditions Time (min) Yielda (%)
Solvent/catalyst (g)/Temp. (°C)
1 H2O/NEST (0.06)/r.t 180 55
2 H2O/NEST (0.06)/Reflux 120 58
3 EtOH/NEST (0.06)/r.t 60 75
4 EtOH/NEST (0.06)/Reflux 60 80
5 H2O:EtOH (1:1)/NEST (0.06)/r.t 45 83
6 H2O:EtOH (1:1)/NEST (0.06)/Reflux 30 85
7 –/NEST (0.06)/35 90 77
8 –/NEST (0.06)/60 150 70
9 –/–/r.t 30 25
10 –/NEST (0.02)/r.t 45 85
11 –/NEST (0.04)/r.t 20 90
12 –/NEST (0.06)/r.t 15 94
13 –/NEST (0.1)/r.t 20 89
  1. Reaction was performed with ethyl acetoacetate (1 mmol), 4-chlorobenzaldehyde (1 mmol), malononitrile (1 mmol), and hydrazine hydrate (2 mmol)
  2. aIsolated yield