708 JOURNAL OF CHEMICAL RESEARCH 2011
Table 2 Optimisation amount of NPs SiO2-H2SO4 on the
reaction of condensation of 3-nitrobenzaldehyde, dimedone
and 2-naphthol in CH2Cl2 at room temperature
Table 3 Effect of the solvent on the reaction between
3-nitrobenzaldehyde, dimedone and 2-naphthol by NPs
SiO2-H2SO4 (0.003 g)
Entry
Catalyst
Time /min
Yielda /%
Entry
Solvent
Time /min
Yielda /%
1
2
3
4
0.001
0.007
0.003
0.01
20
20
20
20
78
97
96
97
1
2
3
4
5
CH2Cl2
H2O
20
20
20
20
40
95
80
77
64
80
EtOH
n-Hexane
Solvent-free
a Isolated yield.
a Isolated yield.
Table 4 Reaction between an aromatic aldehyde, dimedone and 2-naphthol by NPs SiO2-H2SO4 (0.003 g) in CH2Cl2 at room
temperature
Entry
Ar
Product
Time/min
Yield%a
M.p./°C
Found
Reported 18
1
2
C6H5
3-NO2C6H4
4-ClC6H4
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
4n
20
20
20
20
20
20
20
20
20
20
20
20
20
20
82
96
86
87
83
92
83
89
85
95
90
82
91
87
149–151
170–172
180–182
178–180
180–182
202–204
222–224
242–244
270–272
179–181
161–163
177–179
264–266
211–213
151–153
168–170
180–182
179–180
178–180
204–205
223–225
240–241
266–268
178–180
163–165
176–178
263–265
213–215
3
4
2-ClC6H4
5
4-NO2C6H4
4-MeOC6H4
4-OHC6H4
6
7
8
3-OHC6H4
9
5-Br-2-OHC6H3
2,4-Cl2C6H3
2-MeOC6H4
4-MeC6H4
10
11
12
13
14
5-NO2-2-OHC6H3
2-OH-3-MeOC6H3
a Yields refer to the pure isolated products.
The compounds 4a–n were characterised by their H, 13C
NMR and IR spectroscopy and elemental analyses.18
In summary, we prepared NPs SiO2-H2SO4 and have shown
that it has advantages in the preparation of benzo[a]xanthene-
11-ones such as shorter reaction times, simple work-up, and
affords excellent yield. The solid phase acidic catalyst was
re-usable for a number of times without appreciable loss of
activity. The present method does not involve any hazardous
organic solvent. Therefore, this procedure could be classified
as green chemistry.
Received 17 November 2011; accepted 24 November 2011
Paper 1100987 doi: 10.3184/174751911X13230223609418
Published online: 27 December 2011
1
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General procedure:
NPs SiO2-H2SO4 (0.003 g) was added to a stirred mixture of the
aromatic aldehyde (1 mmol), dimedone (1 mmol) and 2-naphthol in
CH2Cl2 (10 mL). The reaction mixture was then stirred for 20 min at
room temperature. The progress of the reaction was followed by TLC
(n-hexane:ethylacetate). After completion of the reaction, the mixture
was filtered to remove the catalyst. After evaporation of the solvent,
the crude product was recrystallised from hot ethanol to obtain the
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We gratefully acknowledge financial support from the Research
Council of Islamic Azad University of Yazd and The Islamic
Azad University of Zahedan of Iran.
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