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L. Wu et al.
DMSO-d6): d = 8.13 (d, 1H, J = 8.0 Hz), 7.98 (d, 1H,
J = 7.6 Hz), 7.89–7.67 (m, 2H), 7.21–7.12 (m, 3H), 6.80–
6.78 (m, 3H), 6.04 (s, 1H), 5.99 (s, 1H), 5.03 (s, 1H), 3.67
(s, 3H) ppm; 13C NMR (100 MHz, CDCl3): d = 178.35,
178.31, 158.39, 157.29, 147.24, 145.63, 143.42, 136.79,
135.07, 131.16, 130.90, 129.98, 129.33, 129.18, 124.49,
116.83, 115.58, 113.91, 108.18, 101.80, 98.41, 55.22,
37.48 ppm.
elemental analyzer. Melting points were determined on a
XT-4 binocular microscope. Commercially available
reagents were used throughout without further purification
unless otherwise stated.
Preparation of the HClO4–SiO2 catalyst
HClO4 (1.8 g, 12.5 mmol, as 70% aqueous solution) was
added to a suspension of SiO2 (230–400 mesh, 23.7 g) in
70.0 cm3 Et2O. The mixture was concentrated and the
residue was heated at 100 °C for 72 h under vacuum to
furnish HClO4–SiO2 (0.5 mmol/g) as a free-flowing
powder (50 mg = 0.025 mmol of HClO4).
12-(4-Methylphenyl)-12H-benzo[i][1,3]dioxolo[4,5-b]xan-
thene-6,11-dione (5d, C25H16O5)
Orange powder, m.p.: 215–216 °C; IR (KBr): m = 2,932,
1,700, 1,644, 1,575, 1,480, 1,373, 1,288, 1,234, 1,186,
1,142, 1,037, 912, 769 cm-1; 1H NMR (400 MHz, DMSO-
d6): d = 8.14 (d, 1H, J = 7.6 Hz), 7.98 (d, 1H,
J = 7.6 Hz), 7.91–7.88 (m, 1H), 7.71–7.68 (m, 1H),
7.19–7.03 (m, 5H), 6.81 (s, 1H), 6.04 (s, 1H), 5.98 (s,
1H), 5.05 (s, 1H), 2.20 (s, 3H) ppm; 13C NMR (100 MHz,
DMSO-d6): d = 178.24, 178.05, 157.51, 147.24, 145.42,
143.16, 142.66, 136.10, 135.46, 131.78, 130.71, 130.66,
129.44, 128.84, 127.90, 124.77, 117.32, 114.78, 108.22,
102.23, 98.99, 37.65, 20.95 ppm.
General procedure for preparation of 5 and 6
A mixture of 3,4-methylenedioxyphenol (1 mmol), aldehyde
(1 mmol), 2-hydroxy-1,4-naphthoquinone or dimedone
(1 mmol), and HClO4–SiO2 (100 mg, 0.05 mmol) was heated
at 110 °C for an appropriate time and monitored by thin-layer
chromatography (TLC) until the final conversion. After
cooling, the reaction mixture was washed with CHCl3 and
filtered to recover the catalyst. The solvent was evaporated and
the crude product purified by silica gel column chromatogra-
phy using CHCl3 as eluent to afford the pure product.
12-(4-Nitrophenyl)-12H-benzo[i][1,3]dioxolo[4,5-b]xan-
thene-6,11-dione (5e, C27H13NO7)
12-Phenyl-12H-benzo[i][1,3]dioxolo[4,5-b]xanthene-6,11-
dione (5a, C24H14O5)
Maroon powder, m.p.: 219–220 °C; IR (KBr): m = 2,991,
1,694, 1,645, 1,604, 1,576, 1,518, 1,481, 1,375, 1,349,
1,290, 1,235, 1,187, 1,144, 1,036, 914, 834 cm-1; 1H NMR
(400 MHz, DMSO-d6): d = 8.17 (d, 1H, J = 8.0 Hz),
8.12–8.10 (m, 2H), 8.00 (d, 1H, J = 7.6 Hz), 7.92–7.88
(m, 1H), 7.74–7.70 (m, 1H), 7.64–7.62 (m, 2H), 7.18 (s, 1H),
Maroon powder, m.p.: 242–243 °C; IR (KBr): m = 1,706,
1,642, 1,607, 1,577, 1,504, 1,481, 1,374, 1,290, 1,188,
1
1,141, 1,031, 913 cm-1; H NMR (400 MHz, DMSO-d6):
d = 8.15 (d, 1H, J = 7.6 Hz), 8.12 (d, 1H, J = 7.6 Hz),
8.04–7.70 (m, 2H), 8.44–7.13 (m, 6H), 6.61 (s, 1H), 6.05
(s, 1H), 5.99 (s, 1H), 5.52 (s, 1H) ppm; 13C NMR
(100 MHz, CDCl3): d = 178.12, 178.10, 158.09, 147.39,
145.56, 142.89, 135.63, 135.12, 132.91, 131.98, 131.38,
130.66, 130.46, 130.17, 130.02, 129.56, 128.24, 127.24,
124.62, 115.70, 107.77, 101.82, 98.42, 35.61 ppm.
6.86 (s, 1H), 6.06 (s, 1H), 6.00 (s, 1H), 5.30 (s, 1H) ppm; 13
C
NMR (100 MHz, CDCl3): d = 178.08, 177.92, 158.07,
151.29, 147.92, 146.72, 146.01, 143.33, 135.29, 131.71,
130.33, 130.00, 129.55, 129.31, 129.20, 124.75, 123.94,
123.63, 114.75, 113.87, 107.91, 102.09, 98.78, 38.35 ppm.
12-(4-Chlorophenyl)-12H-benzo[i][1,3]dioxolo[4,5-b]xan-
thene-6,11-dione (5b, C24H13ClO5)
12-(3-Nitrophenyl)-12H-benzo[i][1,3]dioxolo[4,5-b]xan-
thene-6,11-dione (5f, C27H13NO7)
Maroon powder, m.p.: 229–230 °C; IR (KBr): m = 2,903,
1,701, 1,646, 1,606, 1,502, 1,481, 1,371, 1,288, 1,242, 1,183,
Orange powder, m.p.: 232–233 °C; IR (KBr): m = 2,894,
1,700, 1,644, 1,604, 1,575, 1,528, 1,482, 1,374, 1,350,
1
1,143, 1,035, 935, 909, 776 cm-1; H NMR (400 MHz,
1
1,289, 1,233, 1,188, 1,144, 1,039, 937, 774, 731 cm-1; H
DMSO-d6): d = 8.14 (d, 1H, J = 7.6 Hz), 7.99 (d, 1H,
J = 7.6 Hz), 7.90–7.68 (m, 2H), 7.35–7.13 (m, 5H), 6.82 (s,
1H), 6.05 (s, 1H), 5.99 (s, 1H), 5.12 (s, 1H) ppm; 13C NMR
(100 MHz, CDCl3): d = 178.21, 178.14, 157.59, 147.51,
145.77, 143.37, 142.88, 135.15, 132.73, 131.38, 130.65,
129.99, 129.57, 129.42, 128.72, 126.71, 124.59, 115.93,
114.85, 110.18, 108.06, 101.92, 98.54, 37.80 ppm.
NMR (400 MHz, DMSO-d6): d = 8.19–8.15 (m, 2H),
8.15–7.98 (m, 2H), 7.90–7.531 (m, 4H), 7.16 (s, 1H), 6.86
(s, 1H), 6.05 (s, 1H), 6.00 (s, 1H), 5.32 (s, 1H) ppm; 13C
NMR (100 MHz, CDCl3): d = 178.01, 177.99, 157.97,
148.48, 147.89, 146.30, 146.01, 143.36, 135.29, 134.77,
131.67, 130.38, 130.05, 129.53, 129.44, 124.86, 123.13,
122.16, 114.81, 113.93, 107.94, 102.07, 98.84, 38.27 ppm.
12-(3,4-Dichlorophenyl)-12H-benzo[i][1,3]dioxolo[4,5-
b]xanthene-6,11-dione (5g, C24H12Cl2O5)
12-(4-Methoxylphenyl)-12H-benzo[i][1,3]dioxolo[4,5-
b]xanthene-6,11-dione (5c, C25H16O6)
Orange powder, m.p.: 227–228 °C; IR (KBr): m = 2,975,
1,694, 1,644, 1,608, 1,503, 1,480, 1,374, 1,291, 1,238,
1,144, 1,037, 915, 863 cm-1; 1H NMR (400 MHz, CDCl3):
Maroon powder, m.p.: 201–202 °C; IR (KBr): m = 2,982,
1,736, 1,700, 1,645, 1,606, 1,511, 1,479, 1,372, 1,287,
1
1,255, 1,139, 1,037, 910, 834 cm-1; H NMR (400 MHz,
123