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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

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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