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Table 4 Synthesis of PBT derivatives in the presence of 0.04 g FNAOSiPPEA/Cu(II) at 100 ℃ and solvent-free conditions

From: Preparation and application of FNAOSiPPEA/Cu(II) as a novel magnetite almondshell based Lewis acid-Bronsted base nano-catalyst for the synthesis of pyrimidobenzothiazoles

Entry

R

Time (h)

Yield (%)a

m. p. (°C)

Refs.

1

H

1.15

85

177–179

[32]

2

4-NO2

1

97

171–173

[33]

3

4-Cl

1

95

86–88

[31]

4

4-Br

0.75

97

110–114

[31]

5

4-OH

1.30

84

210–212

[31]

6

2-Cl

2

90

122–123

[6]

7

2-OEt

2.5

89

171–173

[11]

8

2-NO2

1.5

79

122–124

[31]

9

3-NO2

1.20

95

222–223

[6]

10

3-OH

1.5

81

261–262

[6]

11

2,4-(Cl)2

1

87

133–134

[4]

12

2,4-(OMe)2

1.40

77

164–165

[12]

13

3,4-(OH)2

1.40

75

227–229

[6]

  1. Reaction conditions: Aldehyde (1 mmol), 2-aminobenzothiazole (1 mmol), and ethyl acetoacetate (1 mmol), Solvent-free and 100 ℃
  2. aIsolated yield