Entry Product R Time (min) Yield (%) Melting Point, °C
Found Literature
1 3a 8 96 183-185 183-184[33]
2 3b 15 92 310-312 311-312[33]
3 3c 22 96 213-215 214-215[33]
4 3d 18 91 226-228 227-228[33]
5 3e 24 95 259-261 258-259[33]
6 3f 14 90 291-293 289-290[33]
7 3g 20 93 213-215 214-215[33]
8 3h 30 85 180-182 -
9 3i 20 96 177-179 178 -179[32]
10 3j 28 83 183-185 180-182[32]
11 3k 30 92 186-189 185 -187[32]
Table 3: Synthesis of xanthenes catalyzed by KHSO4-SiO2 from 2-naphthols and aldehydes under ultrasonication.