Entry Catalyst Amount of catalyst (mol%) Temp. (°C) Time (h) Yield (%)a Ref.
1 p-TSA 10 125 4 89 9c
2 Sulfamic acid 10 125 8 93 17
3 Poly(4-vinylpyridinium) hydrogen sulfate 2 100 55 min 94 22a
4 Succinimide-N-sulfonic acid 5.6 80 35 min 94 22c
5 Sulfuric acid 10 mg 110-115b 1.5 91 31
6 Cellulose sulfuric acid 80 mg 110-115 1.5 81 31
7 Montmorillonitr K10 300 mg 120 3 75 32
8 Amberlyst-15 10 mg 125 2 94 33
9 Silica sulfuric acid 80 mg 110-115 1.5 89 34
10 Dowex-50W 100 mg 100 1.5 78 35
11 NSPVPHS 10 mg 60 15 min 94 This work
12 NSPVPHS 10 mg Utrasonic method  at r.t. 5 min 95 This work
a Isolated yields
b Solvent: acetic acid
Table 5: Comparison of our results with the results obtained by other groups in the synthesis of 14-(phenyl)-14H-dibenzo[a,j] xanthene.