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Table 2 The reaction of malononitrile, 4-chlorobenzaldehyde and dimedone in the presence of nano-SiO2/DBN under various conditions

From: Nano-SiO2/DBN: an efficacious and reusable catalyst for one-pot synthesis of tetrahydrobenzo[b]pyran derivatives

Entry Conditions Time (min) Yielda (%)
Solvent/temp (°C)/catalyst (g)
1 H2O/EtOH (1:1)/60/‒ 180 28
2 H2O/60/0.03 30 70
3 EtOH/60/0.03 30 58
4 CHCl3/60/0.03 60 50
5 MeOH/60/0.03 60 70
6 ‒/60/0.03 120 42
7 ‒/80/0.03 90 58
8 H2O/EtOH (1:1)/r.t/0.03 15 10
9 H2O/EtOH (1:1)/40/0.03 15 58
10 H2O/EtOH (1:1)/60/0.03b 15 92
11 H2O/EtOH (1:1)/60/0.01 50 76
12 H2O/EtOH (1:1)/60/0.02 30 80
13 H2O/EtOH (1:1)/60/0.04 20 92
14 H2O/EtOH (1:1)/60/0.05 35 70
  1. Reaction conditions: malononitrile (1 mmol), 4-chlorobenzaldehyde (1 mmol), dimedone (1 mmol) and nano-SiO2/DBN as catalyst
  2. aIsolated yield
  3. bThe modified condition