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Table 2 Synthesis of DHPPs 5(a–o) in the presence of NEST

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

Entry

Ar

Product

Time (min)

Yielda (%)

Mp (°C)

Refs.

1

C6H5

5a

10

92

242–244

[44]

2

2-OCH3C6H4

5b

15

89

226–228

[45]

3

3-O2NC6H4

5c

10

90

210–211

[45]

4

4-H3CC6H44

5d

18

87

204–206

[46]

5

4-O2NC6H4

5e

9

93

239–242

[45]

6

3-BrC6H4

5f

15

94

223–224

[46]

7

4-BrC6H4

5g

12

96

178–180

[45]

8

4-ClC6H5

5 h

10

94

230–232

[44]

9

4-OHC6H4

5i

10

95

222–224

[46]

10

3,4-(OH)C6H3

5j

10

91

225–227

[47]

11

2,4-(Cl)C6H3

5k

20

90

223–225

[46]

12

3-OCH3 4-OH, C6H3

5l

15

92

234–236

[46]

13

4-FC6H4

5m

8

96

212–214

[45]

14

2-Furyl

5n

10

91

228–230

[48]

15

1-Naphthyl

5o

25

88

206–208

[20]

  1. aIsolated yield