Table 1 Optimization of the reaction conditions.

From: The choline chloride/hydroquinone carboxylic acid-based DES as a novel catalyst for the green synthesis of dihydrochromeno[4,3-d]pyrimidinediones

Entry

Catalyst (mmol)

Temp. (°C)

Solvent

Yield (%)

1

0.25

60

-

65

2

0.50

60

-

75

3

0.75

60

-

80

4

1.25

60

-

88

5

1.5

60

-

83

6

1.75

60

-

87

7

1.0

70

-

91

8

1.0

80

-

89

9

1.0

90

-

85

10

1.0

100

-

82

11

1.0

Reflux

EtOH

85

12

1.0

Reflux

H2O

88

13

1.0

Reflux

DMF

89

14

1.0

Reflux

Acetonitrile

90

15

1.0

Reflux

Toluene

78

16

1.0

60

-

95

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