H.R. Shaterian et al. / Journal of Molecular Liquids 162 (2011) 95–99
97
Table 2
Synthesis of 3,4-dihydro-1H-benzo[b]xanthene-1,6,11(2H,12H)-triones.
Entry
Substrate
IL1
IL2
Time
(min)
Yield
(%)a,b
Time
(min)
Yield
(%)a,b
L
Benzaldehyde
30
25
35
30
25
35
35
40
35
84
90
80
87
88
83
78
93
78
20
15
15
10
10
7
20
15
10
92
97
97
83
80
95
92
97
97
M
N
O
P
Q
R
S
4-Nitrobenzaldehyde
4-Methylbenzaldehyde
4-Cholorobenzaldehyde
3-Nitrobenzaldehyde
4-Bromobenzaldehyde
4-Fluorobenzaldehyd
2-Cholorobenzaldehyde
3-Bromobenzaldehyde
Scheme 3. Preparation of Brønsted acidic ionic liquid (BAIL), (4-sulfobutyl)tris(4-
T
sulfophenyl)phosphonium hydrogen sulfate (IL2).
a
Yields refer to the pure isolated products.
b
The structure of all known products were confirmed by comparison of their spectral
data (FT-IR, 1H NMR, 13C NMR) with those of known samples in the literature [27].
2-pyrrolidonium hydrogen sulfate (0.08 g, 40 mol%, 0.4 mmol) or (4-
sulfobutyl)tris(4-sulfophenyl)phosphonium hydrogen sulfate (0.07 g,
10 mol%, 0.1 mmol) was reacted in an oil bath at 100 °C for the
appropriated times (Tables 1, 2). After completion of the reaction, it
was cooled to room temperature. Then, 5 mL of water was added to
the mixture. The ionic liquid was dissolved in water, and filtered for
separation of the crude product. The separated product was washed
twice with water (2×5 mL). The solid product was purified by
recrystallization procedure in ethanol.
All of the desired product(s) were characterized by comparison of
their physical data with those of known compounds. For recycling the
catalysts, after washing solid products with water completely, the
water containing ionic liquid (IL is soluble in water) was evaporated
under reduced pressure and ionic liquid was recovered and reused.
Select characterizations of the orange-red products j, k, and l are
given below:
(KBr) (υmax, cm−1): 3035, 1700, 1655, 1636, 1617, 1589, 1543, 1507,
1458, 1286, 1213, 1126, 1092; Anal. Calcd (%) for C30H22O6: C, 75.30; H,
4.63; Found: C, 75.27; H, 4.65.
2.3.2. 14-(2,5-dimethoxylphenyl)-14H-dibenzo[a,i]xanthene-8,13-dione
(k)
Orange powder, M.p.: 260 °C;1H NMR (500 MHz, DMSO-d6):
δ=3.63 (s, 3H), 3.92 (s, 3H), 6.11 (s, 1H), 6.61–6.58 (m, 1H), 6.77
(d, J=8.9 Hz, 1H), 6.84 (d, J=2.8 Hz, 1H), 7.37–7.50 (m, 3H), 7.55
(t, J=7.6 Hz, 1H), 7.74–7.80 (m, 3H), 8.09 (d, J=7.6 Hz, 1H), 8.15
(d, J=7.7 Hz, 1H), 8.26 (d, J=8.4 Hz, 1H) ppm; 13C NMR (125 MHz,
DMSO-d6): δ=178.5, 178.18, 157.4, 153.7, 151.1, 147.0, 135.1, 133.4,
131.7, 131.9, 131.1, 130.1, 129.3, 129.1, 128.4, 127.3, 125.4, 124.5,
124.1, 117.5, 117.2, 116.8, 116.2, 113.1, 112.1, 57.0, 55.5, 30.0 ppm; IR
(KBr) (υmax, cm−1): 3034, 1698, 1655, 1637, 1590, 1542, 1508, 1499,
1458, 1289, 1214, 1182, 1155; Anal. Calcd (%) for C29H20O5: C, 77.67; H,
4.50; Found: C, 77.47; H, 4.64.
2.3.1. 14-(3,4,5-trimethoxylphenyl)-14H-dibenzo[a,i]xanthene-8,13-
dione (j)
Orange powder, M.p.: 288–290 °C; 1H NMR (500 MHz, DMSO-d6):
δ=3.71 (s, 3H), 3.73 (s, 6H), 5.83(s, 1H), 6.57 (s, 2H), 7.41–7.56 (m, 4H),
7.74–7.77 (m, 1H), 7.82–7.89 (m, 2H), 7.95 (d, J=8.0 Hz, 1H), 8.06–8.13
(m, 2H) ppm; 13C NMR (125 MHz, DMSO-d6): δ=178.4, 178.38, 157.16,
153.18, 147.35, 138.70, 136.82, 135.21, 131.9, 131.3, 131.12, 130.85,
129.96, 129.7, 129.45, 128.60, 127.56, 125.69, 124.59, 123.84, 116.73,
116.56, 116.34, 105.88, 77.51, 77.09, 77.66, 60.72, 56.11, 35.28 ppm; IR
2.3.3. 12-phenyl-3,4-dihydro-1H-benzo[b]xanthene-1,6,11(2H,12H)-
trione (l)
Orange powder; mp: 264–265 °C.; 1H NMR (500 MHz, DMSO-d6):
δ=0.94 (3H, s), 1.07 (3H, s), 2.15 and 2.31 (2H, s), 2.67 (2H, s), 4.88
(1H, s), 7.10–7.15 (1H, m), 7.21–7.32 (2H, m), 7.43–7.46 (2H), 7.80–
7.91 (3H, m), 7.99–8.07 (1H, m). 13C NMR (125 MHz, DMSO-d6):
δ=26.9, 28.9, 32.4, 32.7, 40.1, 113.6, 124.2, 126.2, 126.5, 127.2, 128.7,
128.8, 129.0, 130.9, 131.4, 134.6, 135.0, 143.2, 149.5, 163.4, 177.5, 183.2,
196.3 ppm. IR (KBr) (υmax, cm−1): 2926, 1678, 1606. Anal. Calcd for
Table 1
Synthesis of 14-aryl-14H-dibenzo[a,i]xanthene-8,13-diones.
Entry Substrate
IL1
IL2
C25H20O4: C, 78.11; H, 5.24%. Found: C, 78.21; H, 5.29%.
Time Yield Time Yield
(min) (%)a (min) (%)a
2.4. Synthesis of aryl-5H-dibenzo[b,i]xanthene-5,7,12,14(13H)-
tetraones
a
b
c
d
e
f
g
h
i
Benzaldehyde
4-Nitrobenzaldehyde
3-Nitrobenzaldehyde
2,4-di Cholorobenzaldehyde
3,4-di Cholorobenzaldehyde
2-Cholorobenzaldehyde
4-Cholorobenzaldehyde
4-Methylbenzaldehyde
35
25
28
30
28
20
25
30
32
37
90
91
96
90
85
90
90
80
83
82
9
7
4
5
7
4
2
8
10
10
92
94
90
88
88
97
96
85
87
89
A stirred mixture of aldehyde (1 mmol), 2-hydroxy-1,4-naphtho-
quinone (2 mmol) and 2-pyrrolidonium hydrogen sulfate (0.08 g,
40 mol%, 0.4 mmol) or (4-sulfobutyl)tris(4-sulfophenyl)phosphoni-
um hydrogen sulfate (0.07 g, 10 mol%, 0.1 mmol) were reacted in an
oil bath at 100 °C for the appropriated times (Table 3). After
completion of the reaction, it was cooled to room temperature.
Then, 5 mL of water was added to the mixture. The ionic liquid was
dissolved in water, and filtered for separation of the crude product.
The separated product was washed twice with water (2×5 mL). The
solid product was purified by recrystallization procedure in ethanol.
All of the desired product(s) were characterized by comparison of
their physical data with those of known compounds. For recycling the
catalysts, after washing solid products with water completely, the
water containing ionic liquid (IL is soluble in water) was evaporated
under reduced pressure and ionic liquid was recovered and reused.
4-Methoxybenzaldehyde
3,4,5-Trimethoxybenzaldehyde
The corresponding 14-aryl-14H-dibenzo[a,i]
xanthene-8,13-diones was synthesized for
the first time
2,5-Dimethoxybenzaldehyde
The corresponding 14-aryl-14H-dibenzo[a,i]
xanthene-8,13-diones was synthesized for
the first time
j
34
86
12
92
k
a
Yields refer to the isolated pure products. The desired pure products were
characterized by comparison of their physical data (melting points, IR, 1H and 13C NMR)
with those of known compounds [25–27]. The reaction was carried out under thermal
solvent-free conditions in an oil bath at 100 °C.