1170
D. W. Cameron and A. G. Riches
m/z 322 (M [37C1], 14%), 320 (M [35C1], 39), 290 (20), 289 (33), 288
(46), 263 (34), 262 (33), 261 (100), 260 (57).
chromatography, with an ethyl acetate/toluene (5 : 95 → 20: 80) solvent
gradient as eluent, gave 1,7-dihydroxy-9,10-anthraquinone (37) (71 mg,
50%) as yellow needles, m.p. 293° (dec.) (lit.17 291–293°). λmax (logε)
270, 283 inf., 390 nm (4.54, 4.38, 3.97). δ [(CD3)2SO] 12.37, s, 1-OH;
11.17, br s, 7-OH; 8.06, d, J 8.6 Hz, H 5; 7.78, app. t, spacings 7.8 Hz,
H3; 7.67, dd, J 7.6, 1.0 Hz, H 4; 7.52, d, J 2.6 Hz, H 8; 7.33, dd, J 8.2,
1.0 Hz, H 2; 7.25, dd, J 8.6, 2.6 Hz, H6.
(1β,4aβ,9aβ)-4a-Acetoxy-9a-chloro-1,3-dimethoxy-1-trimethylsilyl-
oxy-1,4,4a,9a-tetrahydroanthracene-9,10-dione (46)
To a solution of quinone (24) (101 mg) in benzene (5 cm3) was
added diene (9) (167 mg) and the mixture was stirred at room tempera-
ture for 32 h. The solvent was evaporated and the residue was recrys-
tallized from ether/petrol to give the anthracenedione (46) (82 mg,
45%) as colourless needles, m.p. 176–180° (dec.) (Found: C, 55.6; H,
5.6. C21H25ClO7Si requires C, 55.7; H, 5.6%). λmax (logε) (CHCl3) 242,
260sh nm (4.39, 4.29). δ 8.13, m, H8 or H5; 7.88, m, H 8 or H 5; 7.67,
m, H6, H 7; 4.58, br s, H 2; 3.76, dd, J 16.9, 0.7 Hz, H4α; 3.66, s, 3-
OMe; 2.83, s, 1-OMe; 2.58, dd, J 16.9, 1.7 Hz, H4β; 1.75, s, OAc; 0.20,
s, OSiMe3. m/z 421 (M [35Cl]–31,13%), 393 (24), 363 (37), 289 (42),
202 (94), 187 (42), 183 (22), 171 (39), 163 (68), 98 (43), 75 (34), 73
(100).
Reaction of Diene (2) with Quinone (30)
To a solution of quinone (30) (51 mg) in benzene (3 cm3) was added
diene (2) (300 mg) and the mixture was stirred at 50° for 4 days. It was
then evaporated and the residue was treated with zinc dust in acetic acid
as for the formation of (36). The residue was crystallized from ethyl
acetate/petrol to give 7-hydroxy-1-methoxy-9,10-anthraquinone (18)
(22 mg, 48%) as a yellow microcrystalline solid, m.p. 271° (dec.) (lit.20
273°, lit.21 186–187°) (Found: M+•, 254.0577. Calc. for C15H10O4: M+•,
254.0579). δ [(CD3)2SO, 35°] 7.91, m, ArH; 7.82–7.70, m, 2×ArH;
7.51, m, ArH; 7.28, br s, ArH; 7.03, br m, ArH; 3.92, s, OMe. m/z 254
(M, 100%), 225 (38), 139 (30).
(4aβ,9aβ)-4a-Acetoxy-9a-chloro-3-methoxy-4a,9a-dihydro-
anthracene-1,9,10(4H)-trione (47)
Demethylation of 7-Hydroxy-1-methoxy-9,10-anthraquinone (18)
To a solution of adduct (46) (87 mg) in tetrahydrofuran (3 cm3) was
added 0.1 M hydrochloric acid (10 drops) and the mixture was stirred
for 8 h. It was then diluted with water (20 cm3) and extracted into
dichloromethane (2×10 cm3). The extract was washed with water (2×20
cm3), brine (20 cm3), and then dried and evaporated. Recrystallization
of the pale yellow residue from ethyl acetate/petrol gave the
anthracenetrione (47) (57 mg, 86%) as colourless bars, m.p. 170–173°
(Found: C, 58.5; H, 3.9. C17H13ClO6 requires C, 58.6; H, 3.8%). λmax
(logε) (CHCl3) 243, 259sh nm (4.33, 4.28). νmax 1753, 1713, 1663,
1600 cm–1. δ 8.17, m, H 5 or H 8; 7.99, m, H5 or H 8; 7.81–7.73, m, H 6,
H7; 5.35, br s, H 2; 3.85, br s, H 4α; 3.80, s, 3-OMe; 3.19, br s, H4β;
1.96, s, OAc. δ (45°, partial) 5.35, br s, H2; 3.85, br d, J 17.3 Hz, H4α;
3.80, s. OMe; 3.19, br d, J 17.3 Hz, H4β; 1.95, s, OAc. m/z (15 eV) 305
(M [35Cl]–COCH3, 24%), 254 (62), 98 (100).
The anthraquinone (18) (10 mg) was added to a molten mixture of
aluminium chloride (5 g) and sodium chloride (1 g) at 140°. After 5 min
the reaction mixture was poured onto a mixture of ice (100 g) and con-
centrated hydrochloric acid (5 cm3). The resultant suspension was then
extracted with ethyl acetate (2×50 cm3). The combined extracts were
washed with water (2×50 cm3), brine (100 cm3), and then dried and
evaporated. The residue was subjected to column chromatography, with
a solvent gradient of ethyl acetate/toluene/acetic acid (0: 99: 1 →
20 : 79 : 1) as eluent, to afford 1,7-dihydroxy-9,10-anthraquinone (37)
(4 mg, 42%) as yellow needles, indistinguishable in chromatographic
and spectroscopic properties from material obtained above.
Reaction of Diene (2) with Quinone (29)
To a solution of quinone (29) (79 mg) in benzene (2 cm3) was added
diene (2) (342 mg) and the mixture was stirred at room temperature for
4 days. The solvent was removed and the residue was treated with zinc
dust in acetic acid as for the formation of (36). The product was sub-
jected to column chromatography as for (37) to give 1,6-dihydroxy-
9,10-anthraquinone (17) (37 mg, 52%) as yellow needles, m.p. >270°
(dec.) (lit.17 270–272°). λmax (logε) 271, 408 nm (4.45, 3.90). δ
[(CD3)2SO] 12.70, s, 1-OH; 11.22, br s, 6-OH; 8.10, d, J 8.5 Hz, H 8;
7.75, app. t, spacings 7.9 Hz, H 3; 7.67, dd, J 7.5, 1.0 Hz, H 4; 7.48, d,
J 2.5 Hz, H 5; 7.34, dd, J 8.5, 1.0 Hz, H 2; 7.24, dd, J 8.5, 2.5 Hz, H 7.
Reductive Aromatization of (47)
Trione (47) (13 mg) was treated with zinc dust in acetic acid as for
the formation of (36) to afford 1-hydroxy-3-methoxy-9,10-
anthraquinone (48) (8 mg, 84%) as a yellow solid, m.p. 187–190° (lit.19
193–194°). δ 12.91, s, OH; 8.32–8.27, m, H5, H 8; 7.83–7.76, m, H 6,
H7; 7.39, d, J 2.7 Hz, H4; 6.72, d, J 2.7 Hz, H2; 3.95, s, OMe.
Reaction of Quinone (25) with Diene (9)
To a solution of the naphthoquinone (25) (103 mg) in benzene (1
cm3) was added diene (9) (286 mg) and the mixture was stirred at room
temperature for 48 h. The solvent was evaporated. Trituration of the
residue with ether/petrol gave (1β,4aβ,9aβ)-4a,9a-diacetoxy-1,3-
dimethoxy-1-trimethylsilyloxy-1,4,4a,9a-tetrahydroanthracene-9,10-
dione (51) (2 mg, 1%) as a colourless solid. δ 8.17, m, H5, H8; 7.82, m,
H6, H7; 4.59, br s, H2; 3.73, dd, J 16.9, 0.6 Hz, H4α; 3.67, s, 3-OMe;
2.82, s, 1-OMe; 2.39, d, J 16.9, 1.7 Hz, H4β; 2.19, 1.67, s, s, 2×OAc;
0.24, s, OSiMe3. The remainder of the residue was subjected to prepar-
ative t.l.c., with ethyl acetate/petrol (1 :1) as eluent, to give two bands.
The more mobile, yellow band gave methyl 4-(3´-acetoxy-1´,4´-
dioxo-1´,4´-dihydronaphthalen-2´-yl)-3-methoxybut-2-enoate (49) (45
mg, 32%) as pale yellow needles from ethyl acetate/petrol, m.p.
154–158° (Found: C, 62.7; H, 4.9. C18H16O7 requires C, 62.8; H, 4.7%).
λmax 247, 252, 267, 271, 340 nm. νmax 1765, 1742, 1707, 1671, 1642,
1620, 1592sh cm–1. δ 8.16–8.08, m, H5´, H8´; 7.78–7.71, m, H6´,
H7´; 5.13, br s, H2; 4.29, br s, CH2; 3.72, 3.54, s, s, 2×OMe; 2.32, s,
OAc. m/z 344 (M, 9%), 302 (23), 285 (26), 271 (21), 270 (24), 243
(100), 242 (40), 214 (24), 199 (39), 183 (31), 128 (21), 127 (29), 115
(40), 105 (22), 104 (26), 102 (24).
Reaction of Diene (2) with Quinone (31)
To a solution of quinone (31) (93 mg) in benzene (3 cm3) was added
diene (2) (523 mg) and the mixture was stirred at 50° for 3 days and
then evaporated. Examination of the residue by 1H n.m.r. spectroscopy
showed it to consist of a mixture of two stoichiometric cycloadducts
(1: 1). This mixture was treated with zinc and acetic acid as for the for-
mation of (36). The crude aromatized product was then directly
demethylated by treatment with molten aluminium chloride/sodium
chloride as above. Column chromatography afforded a 1: 1 mixture of
1,6-dihydroxy-9,10-anthraquinone (17) and 1,7-dihydroxy-9,10-
1
anthraquinone (37) [35 mg, 44% from (31)], as shown by H n.m.r.
spectroscopy.
Methyl 4-(3´-Chloro-1´,4´-dioxo-1´,4´-dihydronaphthalen-2´-yl)-3-
methoxybut-2-enoate (45)
To a solution of 2,3-dichloro-1,4-naphthoquinone (44) (93 mg) in
benzene (2 cm3) was added diene (9)2 (150 mg) and the mixture was
stirred for 12 h. Further diene (83 mg) was added and stirring was con-
tinued for 8 h. The solvent was then evaporated and the residue crystal-
lized from ethyl acetate/petrol to give the ester (45) (59 mg, 45%) as
pale yellow bars, m.p. 132–133° (Found: C, 60.0; H, 4.1. C16H13ClO5
requires C, 59.9; H, 4.1%). λmax (logε) 243, 275, 337 nm (4.33, 4.20,
3.40). νmax 1703, 1673, 1614, 1589sh cm–1. δ 8.15, m, H 5´, H8´; 7.76,
m, H 6´, H 7´; 5.18, br s, H 2; 4.51, br s, CH2; 3.74, 3.57, s, s, 2×OMe.
The less mobile, colourless band gave (4aβ,9aβ)-4a,9a-diacetoxy-
3-methoxy-4a,9a-dihydroanthracene-1,9,10(4H)-trione (50) (7 mg,
5%) as colourless crystals from ethyl acetate/petrol, m.p. 163–165°
(Found: C, 61.3; H, 4.4. C19H16O8 requires C, 61.3; H, 4.3%). λmax
(logε) 240, 275sh nm (4.23, 3.87). δ 8.13, d, J 7.9 Hz, H5 or H8;
7.76–7.69, m, H5 or H8, H6 or H7; 7.55, app. dt, J 8.0, 1.9 Hz, H6 or