Introduction
Experimental section
Materials
Apparatus
Preparation of catalyst
Preparation of nano-Fe3O4
Preparation of nano-Fe3O4@SiO2
Preparation of Fe3O4@SiO2–SO3H
General procedure for the synthesis of 1,8-dioxo-octahydroxanthenes
Results and discussion
Characterization of Fe3O4@SiO2–SO3H as solid acid catalyst
Evaluation of the catalytic activity of Fe3O4@SiO2–SO3H in the synthesis 1,8-dioxo-octahydro-xanthenes
Entry | Catalyst loading (g) | Time (min) | Yielda (%) |
---|---|---|---|
1 | – | 30 | 0 |
2 | 0.02 | 15 | 45 |
3 | 0.03 | 15 | 55 |
4 | 0.04 | 15 | 75 |
5 | 0.05 | 4 | 97 |
6 | 0.06 | 4 | 97 |
Entry | Aldehyde (R)
| Product | Time (min) | Yield | M.p. (°C) |
---|---|---|---|---|---|
1 | C6H5
|
3a
| 4 | 97 | 202–203 |
2 |
o-Cl·C6H4
|
3b
| 8 | 90 | 225–226 |
3 |
p-Cl·C6H4
|
3c
| 5 | 95 | 231–233 |
4 | 2,4-Cl2·C6H3
|
3d
| 7 | 92 | 250–252 |
5 |
o-NO2·C6H4
|
3e
| 8 | 89 | 256–258 |
6 |
m-NO2·C6H4
|
3f
| 5 | 90 | 171–172 |
7 |
p-NO2·C6H4
|
3g
| 4 | 96 | 224–226 |
8 | 4-Cl-3-NO2·C6H3
|
3h
| 6 | 94 | 251–253 |
9 |
o-OH·C6H4
|
3i
| 8 | 88 | 231–233 |
10 |
p-OH·C6H4
|
3j
| 4 | 93 | 247–248 |
11 |
p-Me·C6H4
|
3k
| 5 | 95 | 223–224 |
12 |
m-OMe·C6H4
|
3l
| 6 | 93 | 181–182 |
13 |
p-OMe·C6H4
|
3m
| 4 | 95 | 245–247 |