14
I. Drivas et al. / Dyes and Pigments 88 (2011) 7e17
contained a mixture of 10a and 10b and was dissolved in dichloro-
methane (100 cm3). Compound 10a was extracted into sodium
hydroxide (1M, 2 ꢂ 20 cm3) which was then neutralised to give the
product: 10a (3.53 g, 13.2 mmol, yield: 63%). m.p. 182e185 ꢀC;
(Found: C, 70.4; H, 4.5; C16H12O4 requires C, 71.6; H, 4.5%); nmax
(solid)/cm-1 (CeH) 3094e2891, (eOH) 3000e2600, (C]O) 1660,
(CeO) 1272; 1H nmr, dH (300 MHz, (CD3)2SO); 12.71 (1H, s, CeOH),
8.22e8.11 (2H, m, H-5,8), 7.92 (2H, m, H-6,7), 7.69 (1H, d, J 7.5, H-4),
7.40 (1H, d, J 8.4, H-3), 4.19 (2H, q, J 6.6, H-15), 1.40 (3H, t, J 6.6, H-16);
13C {1H} nmr, dC (75 MHz, CDCl3); 189.6 (C]O, C-9), 181.9 (C]O,
C-10), 153.9 (quat. Ar.C, C-2), 153.3 (quat. Ar.C, C-1), 135.1 (Ar.C, C-6),
134.5 (quat. Ar.C, C-12),134.2 (Ar.C, C-7),133.8 (quat. Ar.C, C-11),127.8
(Ar.C, C-5), 127.3 (Ar.C, C-8), 125.5 (quat. Ar.C, C-14), 121.5 (Ar.C, C-3),
117.0 (Ar.C, C-4), 116.5 (quat. Ar.C, C-13), 65.3 (OeCH2CH3, C-15), 15.0
(OeCH2CH3, C-16); m/z (ESI) 291 (100%, MNaþ); UV/vis lmax
(CH3COCH3) 425 nm.
Evaporation of the remaining dichloromethane solution in vacuo
gave a solid, which was further dried in a high vacuum to give 10b:
(1.18 g, 3.98 mmol, yield: 19%). m.p. 129e132 ꢀC; (Found: C, 73.1; H,
5.2; C18H16O4 requires C, 73.0; H, 5.4%); nmax (solid)/cmꢁ1 (CeH)
3084e2893, (C]O) 1669, (CeO) 1264; 1H nmr, dH (300 MHz,
(CD3)2SO); 8.27e8.17 (2H, m, H-5,8), 8.04e7.92 (3H, m, H-4,6,7),
7.57 (1H, d, J 6.0, H-4), 4.24 (2H, q, J 6.6, H-15), 4.15 (2H, q, J 6.9, H-
17), 1.45 (6H, m, H-16,18); dC (75 MHz, CDCl3); 182.7 (C]O, C-9),
182.5 (C]O, C-10), 158.8 (quat. Ar.C, C-2), 149.1 (quat. Ar.C, C-1),
135.3 (quat. Ar.C, C-12), 134.1 (Ar.C, C-6), 133.8 (Ar.C, C-7), 133.1
(quat. Ar.C, C-11), 127.3 (Ar.C, C-5), 126.6 (Ar.C, C-8), 125.0 (Ar.C, C-
3), 121.1 (quat. Ar.C, C-14), 116.9 (Ar.C, C-4), 116.8 (quat. Ar.C, C-13),
69.8 (OeCH2CH3, C-17), 64.9 (OeCH2CH3, C-15), 15.7 (OeCH2CH3,
C-18), 14.7 (OeCH2CH3, C-16); m/z (ESI) 319 (100%, MNaþ); UV/vis
lmax (CH3COCH3) 375 nm.
2-(Benzyloxy)-1-hydroxyanthracene-9,10-dione (11a). Powdered
potassium hydroxide (82 mmol) was added to DMSO (82 cm3) at 37 ꢀC.
After stirring for 5 min, alizarin (41 mmol) was added, followed
immediately by the benzylbromide (CAUTION: Irritating to eyes,
respiratory system and skin) (37.5 mmol). Stirring was continued for
24 h, after which time the mixture was poured into aqueous hydro-
chloric acid (1M, 400 cm3) and extracted with dichloromethane
(3 ꢂ 400 cm3). The combined organic extracts were washed with water
(5 ꢂ 500 cm3), dried (MgSO4) and concentrated in vacuo. The residue
was dried further under high vacuum (24 h). The solid contained
a mixture of 11a, 11b and alizarin (1). The mixture was recrystallised
repeatedly from ethylacetate (CAUTION: Highly flammable. Irritating
to eyes) to give the product 11a (2.3 g, 6.96 mmol, yield: 17%). m.p.
170e174 ꢀC; (Found: C, 75.5; H, 4.2; C21H14O4 requires C, 76.4; H, 4.3%);
nmax (solid)/cmꢁ1 (CeH) 3057e2900, (eOH) 2900e2600, (C]O) 1667,
(CeO) 1262; 1H nmr, dH (300 MHz, (CD3)2SO); 12.75 (1H, s, CeOH),
8.23e8.18 (2H, m, H-5,8), 7.93 (2H, m, H-6,7), 7.73 (1H, d, J 9.0, H-4),
7.56e7.40 (6H, m, H-3,16-21), 5.29 (2H, s, H-15); 13C {1H} nmr, dC
(75 MHz, CDCl3); 189.2 (C]O, C-9),181.5 (C]O, C-10),153.3 (quat. ArC,
C-2),153.1(quat. ArC, C-1),135.7 (quat. ArC, C-16),134.8 (ArC, C-6),134.1
(quat. ArC, C-12), 133.8 (ArC, C-7), 133.4 (quat. ArC, C-11), 128.8 (2 ArC,
C-18,20),128.4 (ArC, C-19),127.4 (2 ArC, C-17,21),127.4 (ArC, C-5),126.9
(ArC, C-8),125.7 (quat. ArC, C-14),120.8 (ArC, C-3),118.1 (ArC, C-4),116.4
(quat. ArC, C-13), 71.2 (eOeCH2ePh, C-15); m/z (ESI) 353 (100%,
MNaþ); UV/vis lmax (CH3COCH3) 423 nm.
vacuum (24 h). The solid contained a mixture of 11a, 11b and
alizarin (1) and was dissolved in dichloromethane (100 cm3). The
compound 11a and alizarin were removed by extraction with
sodium hydroxide (1M, 2 ꢂ 20 cm3). Concentration of the
dichloromethane solution in vacuo gave a solid, which was further
dried in a high vacuum and was proven to be 11b (1.92 g,
4.52 mmol, yield: 11%). m.p. 144-147 ꢀC; (Found: C, 78.4; H, 4.6;
C28H20O4 requires C, 80.0; H, 4.8%); nmax (solid)/cmꢁ1) (CeH)
3067e2873, (C]O) 1668, (CeO) 1260; 1H nmr, dH (300 MHz,
(CD3)2SO); 8.21e8.15 (2H, m, H-5,8), 8.06 (1H, d, J 9.0, H-4),
7.95e7.88 (2H, m, H-6,7), 7.69 (1H, d, J 9.0, H-3), 7.50e7.32 (10H, m,
H-17-21,24-28), 5.32 (2H, s, H-22), 5.04 (2H, s, H-15); 13C {1H} nmr,
dC (75 MHz, CDCl3); 181.6 (C]O, C-9), 181.4 (C]O, C-10), 157.4
(quat. ArC, C-2), 147.6 (quat. ArC, C-1), 136.1 (quat. ArC, C-23), 134.6
(quat. ArC, C-16), 134.2 (quat. ArC, C-12), 132.8 (ArC, C-6), 132.4
(ArC, C-7),132.0 (quat. ArC, C-11),128.0e125.6 (10 ArC),124.5 (quat.
ArC, C-14), 124.2 (ArC, C-3), 116.8 (ArC, C-4), 116.8 (quat. ArC, C-13),
74.2 (eOeCH2ePh, C-22), 70.2 (eOeCH2-Ph, C-15); m/z (ESI) 443
(100%, MNaþ); UV/vis lmax (CH3COCH3) 375 nm.
Methyl-4-(9,10-dihydro-1-hydroxy-9,10-dioxoanthracen-2-
yloxy)butanoate
(12a).
Powdered potassium
hydroxide
(160 mmol) was added to DMSO (80 cm3) at 37 ꢀC. After stirring for
5 min, alizarin (40 mmol) was added, followed immediately by the
methyl-4-bromobutyrate (CAUTION: Harmful if swallowed. Irri-
tating to skin) (100 mmol). Stirring was continued for 72 h, after
which time an additional amount of methyl-4-bromobutyrate was
added (100 mmol). The mixture was stirred for another 24 h and
then it was poured into aqueous hydrochloric acid solution (1M,
400 cm3) and extracted with dichloromethane (3 ꢂ 400 cm3). The
combined organic extracts were washed with water (5 ꢂ 500 cm3),
dried (MgSO4) and concentrated in vacuo. The residue was dried
further under high vacuum (24 h). The solid contained a mixture of
12a, traces of di-derivative (12b) and alizarin (1). The mixture and
was recrystallised twice from ethylacetate to give the product 12a:
(3.2 g, 9.4 mmol, yield: 23%). m.p. 145e148 ꢀC; (Found: C, 66.9; H,
4.7; C19H16O6 requires C, 67.1; H, 4.7%); nmax (solid)/cmꢁ1 (CeH)
3100e2885, (eOH) 3000e2600, (C]O) 1730e1667, (CeO) 1278; 1H
nmr, dH (300 MHz, CDCl3); 13.1 (1H, s, CeOH), 8.32e8.30 (2H, m, H-
5,8), 7.85 (1H, d, J 8.4, H-4), 7.82e7.79 (2H, m, H-6,7), 7.18 (1H, d, J
8.4, H-3), 4.22 (2H, t, J 6.3, H-15), 3.71 (3H, s, H-19), 2.61 (2H, t, J 6.9,
H-17), 2.25 (2H, qu, J 6.6, H-16); 13C {1H} nmr, dC (75 MHz, CDCl3);
189.2 (C]O, C-9), 181.5 (C]O, C-10), 173.4 (quat. eCH2COOCH3, C-
18), 153.4 (quat. ArC, C-2), 153.1 (quat. ArC, C-1), 134.8 (ArC, C-6),
134.2 (quat. ArC, C-12), 133.8 (ArC., C-7), 133.4 (quat. ArC, C-11),
127.4 (ArC, C-5), 126.9 (ArC, C-8), 125.5 (quat. ArC, C-14), 121.0 (ArC,
C-3), 117.2 (ArC, C-4), 116.3 (quat. ArC, C-13), 68.2 (eOCH2CH2CH2-,
C-15), 51.8 (eCH2COOCH3, C-19), 30.3 (eCH2COOCH3, C-17), 24.3
(eCH2CH2CH2-, C-16); m/z (ESI) 363 (100%, MNaþ); UV/vis lmax
(CH3COCH3) 424 nm. Through the work conducted herein, it was
not possible to synthesise significant quantities of the di-derivative
product (12b).
2-Ethoxy-1,4-dihydroxyanthracene-9,10-dione (13a). Powdered
potassium hydroxide (77.6 mmol) was added to DMSO (50 cm3) at
37 ꢀC. After stirring for 5 min, purpurin (19.5 mmol) was added, fol-
lowed immediately by the ethyl iodide (23.4 mmol). Stirring was
continued for 72 h, after which the mixture was poured into hydro-
chloric acid (1M, 400 cm3) and extracted with dichloromethane
(3 ꢂ 400 cm3). The combined organic extracts were washed with
distilled water (5 ꢂ 500 cm3), dried (MgSO4) and concentrated
in vacuo. The residue was dried further under high vacuum (24 h). The
solid contained 13a as well as impurities. Column chromatography,
using DCM as eluent gave 13a (1.90 g, 6.68 mmol, yield: 34%). m.p.
199e201ꢀC; (Found: C, 67.6; H, 4.2; C16H12O5 requiresC,67.6;H, 4.2%);
nmax (solid)/cmꢁ1 (CeH) 2987, (eOH) 3000e2600, (C]O) 1619, (CeO)
1281; 1H nmr, dH (300 MHz, (CD3)2SO); 13.49 (1H, s, C(-4)eOH), 13.22
1,2-Bis(benzyloxy)anthracene-9,10-dione (11b). Powdered
potassium hydroxide (164 mmol) was added to DMSO (82 cm3) at
37 ꢀC. After stirring for 5 min, alizarin (41 mmol) was added, fol-
lowed immediately by the benzylbromide (102.5 mmol). Stirring
was continued for 24 h, after which the mixture was poured into
aqueous hydrochloric acid (1M, 400 cm3) and extracted with
dichloromethane (3 ꢂ 400 cm3). The combined organic extracts
were washed with distilled water (5 ꢂ 500 cm3), dried (MgSO4) and
concentrated in vacuo. The residue was dried further under high