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Table 2 Synthesis of DHPPs 5(ao) 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