C.-F. Chang et al. / Tetrahedron 64 (2008) 3661e3666
3665
0.2 mmol) were added and the suspension was heated at 70 ꢀC
4.14. 5,7-Diacetoxy-3-(2,4,5-tribenzyloxyphenyl)chromen-
2-one (14a)
for 1 h. The solvent was removed in vacuo, and the residue
was chromatographed on a silica gel column (CH2Cl2/EtOAc
1:1) to give 1 (0.025 g, 81%) as a white solid; mp>300 ꢀC
From bromocoumarin 9 (0.20 g, 0.6 mmol) and 13a (0.60 g,
0.9 mmol), 14a was obtained in 66% (0.25 g, 0.4 mmol) yield
1
(lit.4 mp>300 ꢀC). H NMR (CDCl3þDMSO-d6) d 3.85 and
1
3.89 (s, 6H), 6.54 (br s, 2H), 7.03 (dd, J¼8.4, 2.1 Hz, 1H),
7.24 (d, J¼2.1 Hz, 1H), 7.91 (d, J¼8.4 Hz, 1H); 13C NMR
(CDCl3þDMSO-d6) d 54.6, 54.7, 92.2, 95.8, 95.9, 97.5,
100.8, 112.0, 115.0, 119.6, 154.2, 154.7, 155.2, 157.3, 157.6,
159.3, 161.8; HRMS (ESI) calcd for C17H12O6 (neg)
312.0634, found 312.0623.
as a yellow solid; mp 141e142 ꢀC. H NMR (CDCl3) d 2.24
and 2.32 (s, 6H), 4.95, 5.12, and 5.14 (s, 6H), 6.68 and 7.10
(s, 2H), 6.95 and 7.02 (d, J¼1.8 Hz, 2H), 7.25e7.46 (m,
15H), 7.74 (s, 1H); 13C NMR (CDCl3) d 20.7, 21.1, 71.5,
71.7, 72.6, 102.6, 107.5, 111.0, 112.0, 116.4, 118.8, 125.0,
127.2, 127.3, 127.6, 127.8, 127.9, 128.0, 128.4, 128.5, 128.6,
135.0, 136.7, 136.8, 137.2, 142.9, 147.0, 150.5, 151.5, 152.1,
154.2, 159.7, 168.1, 168.4; HRMS (EI) calcd for C40H32O9
(Mþ) 656.2046, found 656.2048.
4.11. 1,3,9-Trimethoxy-benzo[4,5]furo[3,2-c]chromen-
6-one (3)
4.15. 5,7-Diacetoxy-3-(2-benzyloxy-4,5-diisopropyloxy-
phenyl)chromen-2-one (14b)
From 12 (0.03 g, 0.07 mmol) and Me2SO4 (32.0 mL,
0.2 mmol) with K2CO3 (0.020 g, 0.2 mmol), using above pro-
cedure, the coumestan 3 (0.02 g, 87%) was isolated as a white
solid; mp 220e222 ꢀC (lit.4 mp 220e225 ꢀC). 1H NMR
(CDCl3þDMSO-d6) d 3.90 and 4.05 (s, 9H), 6.46 and 6.60
(d, J¼2.1 Hz, 2H), 7.03 (dd, J¼8.7, 2.1 Hz, 1H), 7.22 (d,
J¼2.1 Hz, 1H), 7.87 (d, J¼8.7 Hz, 1H); 13C NMR (CDCl3þ
DMSO-d6) d 55.2, 55.3, 55.7, 93.1, 94.9, 96.1, 97.1, 102.0,
112.7, 115.3, 120.3, 155.2, 155.7, 156.0, 157.7, 158.3, 159.2,
162.4; HRMS (EI) calcd for C18H14O6 (Mþ) 326.0790, found
326.0789.
Compound 14b was prepared from 9 (0.20 g, 0.6 mmol)
and 13b (0.52 g, 0.9 mmol) in 74% (0.24 g, 0.4 mmol) yield
as a yellow-green crystal; mp 158e159 ꢀC. 1H NMR (CDCl3)
d 1.32 and 1.33 (d, J¼6.3 Hz, 12H), 2.24 and 2.31 (s, 6H),
4.36 and 4.51 (hept, J¼6.3 Hz, 2H), 5.04 (s, 2H), 6.64 and
7.01 (s, 2H), 6.96 and 7.03 (d, J¼2.1 Hz, 2H), 7.27e7.40
(m, 5H), 7.81 (s, 1H); 13C NMR (CDCl3) d 20.7, 21.1, 22.1,
22.3, 71.5, 72.1, 73.6, 104.3, 107.5, 111.1, 112.0, 116.5, 122.2,
125.2, 127.2, 127.8, 128.5, 134.9, 136.8, 142.6, 147.0, 150.9,
151.8, 152.0, 154.2, 159.7, 168.2, 168.4. Anal. Calcd for
C32H32O9: C, 68.56; H, 5.75; O, 25.69. Found: C, 68.34; H,
5.69; O, 25.77.
4.12. 2-Benzyloxy-4,5-dibenzyloxyphenyltributyl-
stannane (13a)
4.16. 5,7-Dihydroxy-3-(2,4,5-trihydroxyphenyl)chromen-2-
one (15)
The stannane 13a was prepared, using the previous proce-
dure,9 from the 2,4,5-tribenzyloxyphenyl bromide (1.00 g,
2.1 mmol) in 96% yield (1.39 g, 2.0 mmol) as a colorless
Compound 15 was prepared, using above procedure, from
14a (0.15 g, 0.2 mmol) and TiCl4 (0.11 mL, 1.1 mmol) in
56% yield (0.04 g, 0.1 mmol) as a yellow solid. 1H NMR
[(CD3)2CO] d 6.32 and 6.38 (d, J¼2.1 Hz, 2H), 6.46 and
6.85 (s, 2H), 8.07 (s, 1H), 7.51, 7.77, 7.96, 9.36, and 9.65
(br s, 5H).
1
oil. H NMR [(CD3)2CO] d 0.82 (t, J¼7.5 Hz, 9H), 0.95 (t,
J¼7.8 Hz, 6H), 1.21e1.29 (m, 6H), 1.41e1.50 (m, 6H),
5.02, 5.07, and 5.17 (s, 6H), 6.88 and 6.97 (s, 2H), 7.30e
7.51 (m, 15H); 13C NMR [(CD3)2CO] d 9.4, 13.2, 27.1,
29.0, 70.4, 70.7, 72.4, 99.7, 119.5, 125.1, 127.5, 127.6, 127.6,
127.7, 127.8, 127.9, 128.2, 128.3, 128.4, 137.5, 137.7, 138.3,
143.2, 150.9, 158.5.
4.17. 1,3-Diacetoxy-8,9-diisopropyloxy-benzo[4,5]furo-
[3,2-c]chromen-6-one (16)
4.13. 2-Benzyloxy-4,5-diisopropyloxyphenyltributyl-
stannane (13b)
The 14b (0.30 g, 0.5 mmol) was transformed, using the
general procedure, to generate the corresponding hydroxyaryl
coumarin (0.24 g, 0.5 mmol) in 95% yield as a yellow solid;
1
The product 13b was isolated from the 2-benzyloxy-4,5-
diisopropyloxyphenyl bromide (1.00 g, 2.6 mmol) in 94%
yield (1.46 g, 2.5 mmol) as a colorless oil. 1H NMR
[(CD3)2CO] d 0.97 (t, J¼8.1 Hz, 9H), 1.06 (t, J¼7.8 Hz,
6H), 1.21 and 1.25 (d, J¼6.3 Hz, 12H), 1.21e1.32 (m, 6H),
1.39e1.55 (m, 6H), 4.30 and 4.56 (hept, J¼6.3 Hz, 2H),
5.03 (s, 2H), 6.67 and 6.70 (s, 2H), 7.31e7.47 (m, 5H); 13C
NMR [(CD3)2CO] d 9.3, 13.0, 21.6, 21.7, 27.0, 28.9, 70.2,
70.8, 72.6, 101.5, 119.4, 127.6, 127.7, 128.2, 128.3, 137.5,
142.8, 150.8, 158.6.
mp 165e166 ꢀC. H NMR (CDCl3) d 1.30 and 1.44 (d, J¼
6.3 Hz, 12H), 2.34 and 2.41 (s, 6H), 4.31 and 4.56 (hept,
J¼6.3 Hz, 2H), 6.61 and 6.86 (s, 2H), 7.05 and 7.13
(d, J¼2.1 Hz, 2H), 7.47 (br s, 1H), 7.79 (s, 1H); 13C NMR
(CDCl3) d 20.9, 21.1, 22.0, 22.2, 71.1, 74.4, 106.4, 107.5,
111.2, 112.8, 114.0, 123.2, 126.4, 135.8, 142.2, 147.2,
151.1, 152.5, 152.7, 153.4, 162.7, 168.2, 168.3; HRMS (EI)
calcd for C25H26O9 (Mþ) 470.1577, found 470.1585. Follow-
ing oxidative-cyclization with I2 (1 equiv 0.5 mmol), coume-
stan 16 was isolated in 93% yield (0.22 g, 0.5 mmol) as