First Synthesis of 9,10-Dimethoxy-2-methyl-1,4-anthraquinone
129.1, 125.0, 124.3, 64.0, 52.9, 48.4, 46.3 ppm. HRMS: (ESI, the crystallographic data. S. R. is thankful to the Council of Sci-
70 eV): calcd. for C16H13O4 [M – C5H5]+ 269.0814; found 269.0791.
ence and Industrial Research, New Delhi, for her research fellow-
ship. The 400 MHz NMR instrument and the CCD X-ray dif-
fractometer were purchased under FIST program of the DST, New
Delhi.
1,4-Dihydro-6,11-dimethoxy-1,4-methanonaphthacene-5,12-dione
(23): Compound 22 (50 mg, 0.15 mmol) was dissolved in tert-butyl
alcohol (5 mL) containing potassium tert-butoxide (25 mg,
0.22 mmol). To this mixture was added iodomethane (0.02 mL,
0.30 mmol), and the resulting mixture was stirred at room tempera-
ture for 2 h. The mixture was then diluted with water and extracted
with ethyl acetate (2ϫ20 mL). The combined extracts were washed
successively with water (10 mL), dilute hydrochloric acid (5 mL),
and brine (5 mL). The organic layer was then dried with anhydrous
Na2SO4, filtered, and concentrated under reduced pressure. Col-
umn chromatography of the residue afforded compound 23 as a
light-yellow solid (30 mg, 61%). Rf = 0.60 (ethyl acetate/petroleum
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ether, 1:3). M.p. 150–151 °C. IR (KBr): ν = 2933, 1693, 1349, 1267,
˜
1
1025 cm–1. H NMR (400 MHz, CDCl3, 25 °C): δ = 8.26–8.32 (m,
2 H), 7.67–7.72 (m, 2 H), 6.65 (s, 2 H), 4.06 (s, 6 H), 3.57 (s, 2 H),
3
3
1.65 (d, JH,H = 8.8 Hz, 1 H), 1.60 (d, JH,H = 8.8 Hz, 1 H) ppm.
13C NMR (100 MHz, CDCl3, 25 °C): δ = 191.4, 153.7, 141.4, 133.5,
132.0, 129.3, 124.3, 121.5, 64.4, 42.4, 41.6 ppm. HRMS: (ESI,
70 eV): calcd. for C21H17O5 [M + OH]+ 349.1076; found 349.1073.
1,4-Dihydro-5,12-dihydroxy-6,12-dimethoxy-1,4-methanonaphth-
acene (24): To a stirred solution of diisopropylamine (0.01 mL,
0.18 mmol) in THF (3 mL) cooled to –78 °C was added n-butyllith-
ium (0.15 mL, 0.18 mmol), and the reaction mixture was stirred for
15 min. Compound 22 (50 mg, 0.15 mmol) was added to this mix-
ture. After 20 min at –78 °C, iodomethane (0.05 mL, 0.75 mmol)
was added, and then the mixture was stirred for 1 h. The mixture
was brought to room temperature over 1 h and further stirred for
1–2 h. The reaction mixture was then diluted with water (10 mL)
and extracted with ethyl acetate (2ϫ20 mL). The combined ex-
tracts were washed successively with water (10 mL), dilute hydro-
chloric acid (5 mL), and brine (5 mL). The organic layer was dried
with anhydrous Na2SO4, filtered, and concentrated under reduced
pressure. Column chromatography of the residue on silica gel af-
forded compound 24 as an orange solid (35 mg, 70%). Rf = 0.55
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9,10-Dihydroxy-1,4-anthraquinones have been intercepted by
various chemical reactions like Diels–Alder reaction, Michael
addition, and imine formation of the corresponding quinizarin
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Density functional theory (DFT) with the B3LYP/6-31G(d) ba-
sic set was used for the energy minimization of the compounds.
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(ethyl acetate/petroleum ether, 1:3). M.p. 140–141 °C. IR (KBr): ν
˜
= 3448, 2942, 1648, 1346, 1276 cm–1. 1H NMR (400 MHz, CDCl3,
25 °C): δ = 8.32–8.37 (m, 2 H), 7.65–7.75 (m, 2 H), 6.92 (s, 2 H),
3
4.25 (s, 2 H), 4.06 (s, 6 H), 2.33 (d, JH,H = 6.8 Hz, 1 H), 2.29 (d,
3JH,H = 6.8 Hz, 1 H) ppm. 13C NMR (100 MHz, CDCl3, 25 °C): δ
= 181.0, 163.4, 155.4, 142.5, 132.7, 129.8, 124.9, 120.8, 72.0, 63.0,
48.8 ppm. HRMS: (ESI, 70 eV): calcd. for C16H13O4 [M – H]+
333.1127; found 333.1120.
[9]
[10]
[11]
9,10-Dimethoxyanthracene-1,4-dione (25):[32] This compound was
prepared as a yellow solid in 92% yield from 22 by following the
flash vacuum pyrolytic procedure described above. The product
was purified by column chromatography on silica gel (Rf = 0.50;
ethyl acetate/petroleum ether, 1:3) to furnish 25. M.p. 189–192 °C.
[12]
IR (KBr): ν = 3442, 2933, 1658, 1610, 1561, 1397, 1344, 1079,
˜
1
998 cm–1. H NMR (400 MHz, CDCl3, 25 °C): δ = 8.38–8.43 (m,
2 H), 7.74–7.79 (m, 2 H), 6.91 (s, 2 H), 4.06 (s, 6 H) ppm.
[13]
[14]
Supporting Information (see footnote on the first page of this arti-
cle): Copies of NMR spectra of all new compounds and compara-
tive table for physical data of synthetic and natural 3.
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Acknowledgments
This research was supported by the Department of Science and
Technology (DST), New Delhi. We are thankful to Dr. A. Patra
and Dr. P. Pahari for helpful discussions and to Mr. L. Rajput for
Eur. J. Org. Chem. 2008, 3014–3020
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
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