PAPER
Synthesis of Quinonoid Analogues of Diospyrin
939
(C6¢)a, 114.6 (C8¢)a, 117.5 (C2¢)b, 118.0 (C2)b, 118.2 (C3)a, 120.8
(C6)a, 122.8 (C7¢)c, 131.4 (C7)c, 134.7 (C4a¢)c, 137.2 (C8a¢)c, 139.6
(C8)a, 145.2 (C4a)d, 146.4 (C8a)d, 147.8 (C5¢)d, 153.4 (C1¢)e, 157.4
(C4¢)e, 159.8 (C5)e, 184.3 (C1)f, 184.5 (C4)f.
2-(3,6-Dioxocyclohexa-1,4-dienyl)-7-methyl-1,4-naphtho-
quinone (10a)
Following the typical procedure for 7a using 9a (450 mg, 1.45
mmol), MeCN (40 mL), and H2O (16 mL) with the addition of CAN
(2.4 g, 4.37 mmol), MeCN (25 mL), and H2O (25 mL) over 20 min.
Extraction was with CH2Cl2 (3 × 30 mL) and chromatography
(EtOAc–hexane, 1:4) afforded 10a (290 mg, 71%) as yellow crys-
tals; mp 155–157 °C (EtOH).
HRMS: m/z [M]+ calcd for C26H24O6: 432.1572; found: 432.1546.
Anal. Calcd for C26H24O6: C, 72.2; H, 5.6. Found: C, 72.0; H, 5.8.
5,5¢-Dimethoxy-7,7¢-dimethyl-2,2¢-binaphthalene-1,1¢,4,4¢-
tetrone (7b)
Following the typical procedure for 7a using 6b (250 mg, 0.58
mmol), MeCN (18 mL), and H2O (8 mL) with addition of CAN (1.0
g, 1.80 mmol), MeCN (10 mL), and H2O (10 mL) over 20 min;
chromatography (EtOAc–hexane, 1:1) afforded 7b (151 mg, 65%)
as yellow crystals; mp 219 °C (dec) (EtOAc–hexane).
IR (Nujol): 1668 (s, C=O), 1658 (m, C=O), 1599 (s, Ar), 1580
cm–1 (m, Ar).
1H NMR (200 MHz, CDCl3): d = 2.52 (s, 3 H, 7-CH3), 6.89 (br s, 3
H, H3¢, H5¢, H6¢), 6.97 (s, 1 H, H3), 7.59 (dd, J = 8.0, 2.0 Hz, 1 H,
H6), 7.92 (d, J = 2.0 Hz, 1 H, H8), 8.01(d, J = 8.0 Hz, 1 H, H5).
13C NMR (50 MHz, CDCl3): d = 21.9 (CH3), 126.6 (C5¢)a, 127.4
(C6¢)a, 129.8 (C2¢)b, 131.8 (C2)b, 135.0 (C3¢)c, 135.5 (C6)c, 136.6
(C8)c, 136.9 (C5)c, 138.0 (C3)c, 141.3 (C4a)d, 142.2 (C8a)d, 145.6
(C7)d, 182.9 (C1¢)e, 183.8 (C4¢)e, 184.6 (C1)e, 186.4 (C4)e.
IR (Nujol): 1668 (m, C=O), 1652 cm–1 (m, C=O).
1H NMR (200 MHz, CDCl3): d = 2.49 (s, 6 H, 7¢-CH3, 7-CH3), 4.02
(s, 6 H, 2 OMe), 6.94 (d, J = 1.0 Hz, 2 H, H6¢, H6), 7.13 (s, 2 H, H3¢,
H3), 7.58 (d, J = 1.0 Hz, 2 H, H8¢, H8).
HRMS: m/z [M]+ calcd for C17H10O4: 278.0579; found: 278.0570.
13C NMR (50 MHz, CDCl3): d = 22.5 (7¢-CH3, 7-CH3), 56.6
(2 OMe), 118.6 (C6¢, C6)a, 120.8 (C3¢, C3)a, 131.0 (C2¢, C2)b, 135.1
(C7¢, C7)b, 139.8 (C8¢, C8), 141.1 (C4a¢, 4a)c, 146.9 (C8a¢, 8a)c,
160.0 (C5¢, C5), 183.2 (C1¢, C1)d, 183.5 (C4¢, C4)d.
Anal. Calcd for C17H10O4: C, 73.4; H, 3.6. Found: C, 73.2; H, 3.8.
2-(3,6-Dioxocyclohexa-1,4-dienyl)-5-methoxy-7-methyl-1,4-
naphthoquinone (9b)
Following the typical procedure for 6a using 2b (760 mg, 2.70
mmol), Pd(PPh3)4 (320 mg, 0.28 mmol), and benzene (30 mL) and
aq 2 M Na2CO3 (3.0 mL), 8 (500 mg, 2.70 mmol), and benzene (20
mL); chromatography (EtOAc–hexane, 3:7) afforded 9b (575 mg,
63%) as reddish brown crystals; mp 147–149 °C (EtOH).
HRMS: m/z [M]+ calcd for C24H18O6: 402.1103; found: 402.1247.
Anal. Calcd for C24H18O6: C, 71.6; H, 4.5. Found: C, 71.8; H, 4.6.
2,5-Dimethoxyphenylboronic Acid (8)
Following the typical procedure for 5a using 1.32 M soln of BuLi
(3.84 mL, 5.06 mmol, 1.1 equiv), 2-bromo-1,4-dimethoxybenzene
(1.0g, 4.60 mmol), and THF (10 mL), but stirring the mixture for 10
min, and B(OMe)3(2.58 mL, 2.39 g, 23.00 mmol, 5.0 equiv) with
the mixture allowed to warm to 24 °C over 2 h. 8 (671 mg, 80%)
was obtained as white crystals; mp 86–87 °C (benzene) (Lit.25 91–
93 °C).
IR (Nujol): 1668 (m, C=O), 1649 (s, C=O), 1603 cm–1 (m, Ar).
1H NMR (200 MHz, CDCl3): d = 2.46 (s, 3 H, CH3), 3.71 (s, 3 H,
OMe), 3.77 (s, 3 H, OMe), 3.98 (s, 3 H, OMe), 6.79 (dd, J = 2.4, 0.6
Hz, 1 H, H3¢), 6.86 (s, 1 H, H3), 6.90 (m, 2 H, H5¢, H6¢), 7.08 (d,
J = 2.0 Hz, 1 H, H6), 7.58 (d, J = 2.0 Hz, 1 H, H8).
13C NMR (50 MHz, CDCl3): d = 22.2 (CH3), 55.7 (OMe), 56.3
(2 OMe), 112.5 (C3¢)a, 115.7 (C5¢)a, 116.0 (C6¢)a, 117.7 (C2¢), 117.9
(C6)b, 120.4 (C8)b, 123.9 (C2)c, 134.6 (C7)c, 138.8 (C3)b, 145.3
(C4a)d, 146.1 (C8a)d, 151.4 (C1¢)e, 153.4 (C4¢)e, 159.5 (C5)e, 183.8
(C1)f, 184.2 (C4)f.
IR (Nujol): 3227 (s, OH), 1503 cm–1 (s, Ar).
1H NMR (200 MHz, CDCl3): d = 3.81 (s, 3 H, OMe), 3.88 (s, 3 H,
OMe), 6.38 [br s, 2 H, B(OH)2], 6.85 (d, J = 8.6 Hz, 1 H, H6), 6.99
(dd, J = 8.6, 2.8 Hz, 1 H, H5), 7.39 (d, J = 2.8 Hz, 1 H, H3).
HRMS: m/z [M]+ calcd for C20H18O5: 338.1154; found: 338.1143.
13C NMR (50 MHz, CDCl3): d = 55.8 (OMe), 56.1 (OMe), 111.3,
118.7, 120.8 (C2, C3, C5, C6), 153.9 (C1)a, 158.9 (C4)a.
Anal. Calcd for C20H18O5: C, 71.0; H, 5.4. Found: C, 71.3; H, 5.6.
HRMS: m/z [M]+ calcd for C8H11BO4: 182.0752; found: 182.0755.
2-(3,6-Dioxocyclohexa-1,4-dienyl)-5-methoxy-7-methyl-1,4-
naphthoquinone (10b)
Anal. Calcd for C8H11BO4: C, 52.8; H, 6.1. Found: C, 52.9; H, 6.0.
Following the typical procedure for 7a using 9a (290 mg, 0.86
mmol), MeCN (25 mL), and H2O (10 mL) and CAN (1.44 g, 2.62
mmol), MeCN (15 mL), and H2O (15 mL); chromatography
(EtOAc–hexane, 2:3) afforded 10b (191 mg, 72%) as orange crys-
tals; mp >300 °C (EtOH).
2-(2,5-Dimethoxyphenyl)-7-methyl-1,4-naphthoquinone (9a)
Following the typical procedure for 6a using 2a (700 mg, 2.80
mmol), Pd(PPh3)4 (335 mg, 0.29 mmol), and benzene (30 mL) and
aq 2 M Na2CO3 (3.0 mL), 8 (500 mg, 2.74 mmol), and benzene (20
mL); chromatography (EtOAc–hexane, 1:5) afforded 9a (652 mg,
76%) as reddish brown crystals; mp 63–64 °C (EtOH).
IR (Nujol): 1667 (m, C=O), 1646 (w, C=O), 1597 (w, Ar), 1577
cm–1 (m, Ar).
1H NMR (200 MHz, DMSO-d6): d = 2.42 (s, 3 H, 7-CH3), 3.90 (s,
3 H, 5-OMe), 7.03 (dd, J = 8.8, 2.6 Hz, 1 H, H5¢), 7.34 (d, J = 2.0
Hz, 1 H, H6), 7.39 (d, J = 2.6 Hz, 1 H, H3¢), 7.48 (s, 1 H, H3), 7.66
(d, J = 8.8 Hz, 1 H, H6¢), 9.91 (d, J = 2.0 Hz, 1 H, H8).
13C NMR (50 MHz, DMSO-d6): d = 21.7 (CH3), 56.3 (OMe), 106.3
(C5¢)a, 113.5 (C6¢)a, 116.7 (C2¢)b, 118.3 (C3¢)a, 119.4 (C2)b, 119.8
(C3)c, 120.8 (C7)c, 122.9 (C6)c, 134.9 (C8)c, 146.9 (C4a)d, 149.5
(C8a)d, 154.7 (C5), 155.8 (C1¢)e, 160.5 (C4¢)e, 173.4 (C1)f, 180.8
(C4)f.
IR (Nujol): 1663 (s, C=O), 1655 (m, C=O), 1599 cm–1 (s, Ar).
1H NMR (200 MHz, CDCl3): d = 2.51 (s, 3 H, 7-CH3), 3.74 (s, 3 H,
OMe), 3.79 (s, 3 H, OMe), 6.81 (d, J = 2.6 Hz, 1 H, H3¢), 6.94 (s, 1
H, H3)a, 6.94 (m, 1 H, H6¢)a, 6.97 (m, 1 H, H5¢)a, 7.56 (dd, J = 8.2,
2.0 Hz, 1 H, H6), 7.94 (d, J = 2.0 Hz, 1 H, H8), 8.01 (d, J = 8.2 Hz,
1 H, H5).
13C NMR (50 MHz, CDCl3): d = 21.8 (CH3), 55.8 (OMe), 56.4
(OMe), 112.6 (C3¢)a, 115.9 (C6¢)a, 116.1 (C5¢)a, 124.4 (C2¢)b, 126.2
(C3)c, 127.3 (C6)c, 130.0 (C2)b, 132.5 (C7)b, 134.3 (C8)c, 136.8
(C5)c, 144.8 (C4a)d, 147.8 (C8a)d, 151.5 (C1¢)e, 153.5 (C4¢)e, 183.7
(C1)f, 185.1 (C4)f.
HRMS: m/z [M]+ calcd for C18H12O5: 308.0684; found: 308.0611.
Anal. Calcd for C18H12O5: C, 70.1; H, 3.9. Found: C, 70.2; H, 4.0.
HRMS: m/z [M]+ calcd for C19H16O4: 308.1048; found: 308.1049.
Anal. Calcd for C19H16O4: C, 74.0; H, 5.2. Found: C, 74.2; H, 5.0.
Synthesis 2009, No. 6, 935–940 © Thieme Stuttgart · New York