4
TSAI ET AL.
120.4, 120.0, 118.3, 112.6, 111.8, 55.7. HRMS (ESI) calcd.
For C16H12BrO3 [M + H]+ 330.9970. Found: 330.9960.
Mp 119–120ꢀC. 1H NMR (600 MHz, CDCl3) δ 12.0 (s,
1H), 8.55 (d, J = 2.4 Hz, 1H), 7.78 (d, J = 7.9 Hz, 1H),
7.73 (d, J = 0.6 Hz, 1H), 7.63 (dd, J = 8.9 Hz, 2.4 Hz, 1H),
7.55 (td, J = 9.2, 1.1 Hz, 1H), 7.38 (td, J = 7.9, 0.6 Hz,
1H), 6.99 (d, J = 8.9 Hz, 1H). 13C NMR (150 MHz, CDCl3)
δ 185.5, 162.5, 156.2, 151.8, 139.1, 133.9, 128.9, 126.6,
124.4, 123.4, 120.5, 120.1, 117.3, 112.6, 110.9. HRMS (ESI)
calcd. For C15H10BrO3 [M + H]+ 316.9813. Found:
316.9807.
3.3 | (5-Bromobenzofuran-2-yl)
(2-hydroxyphenyl)methanone (6)
Compound 5 (0.3208 g, 1.0052 mmol) was treated with
the same procedure as described in preparation of 3. Puri-
fication by flash column chromatography (EtOAc:Hex-
ane = 0:1–1:20–1:10; EtOAc:Hexane = 3:10, Rf = 0.7)
afforded 6 (0.0510 g, 0.161 mmol) as a yellow solid. Yield:
3.6 | Benzofuran-2-yl(5-bromo-
2-methoxyphenyl)methanone (12)
1
16%. Mp 130–133ꢀC. H NMR (600 MHz, CDCl3) δ 11.95
(s, 1H), 8.35 (d, J = 8.0 Hz, 1H), 7.89 (s, 1H), 7.62–7.60
(br s, 2H), 7.57 (d, J = 7.5 Hz, 1H), 7.55 (t, J = 9.0 Hz,
1H), 7.26 (s, 1H), 7.08 (d, J = 8.3 Hz, 1H), 7.02 (t,
J = 7.7 Hz, 1H). 13C NMR (150 MHz, CDCl3) δ 186.4,
163.6, 154.6, 153.1, 136.9, 131.7, 131.4, 128.6, 125.7, 119.3,
118.8, 118.7, 117.3, 115.4, 114.0. HRMS (ESI) calcd. For
C15H10BrO3 [M + H]+ 316.9813. Found: 316.9809.
Compound 11 (0.0447 g, 0.141 mmol) was treated with
the same procedure as described in preparation of 7 in
which acetone was replaced of DMF. Purification by flash
column chromatography (EtOAc:Hexane = 1:10–1:8;
EtOAc:Hexane = 1:10, Rf = 0.3) afforded 12 (0.0362 g,
0.110 mmol) as a yellow gum. Yield: 78%. 1H NMR
(600 MHz, CDCl3) δ 7.70 (d, J = 8.0 Hz, 1H), 7.61–7.59
(m, 3H), 7.49 (td, J = 8.4 Hz, 1.1 Hz, 1H), 7.35 (d,
J = 0.7 Hz, 1H), 7.32 (td, J = 7.8, 0.7 Hz, 1H), 6.92 (d,
J = 9.0 Hz, 1H), 3.79 (s, 3H). 13C NMR (150 MHz, CDCl3)
δ 183.2, 156.7, 156.2, 152.5, 135.0, 132.1, 129.6, 128.7,
127.1, 124.0, 123.5, 116.8, 113.6, 112.6, 56.1. HRMS (ESI)
calcd. For C16H12BrO3 [M + H]+ 330.9970. Found:
330.9966.
3.4 | (5-Bromobenzofuran-2-yl)
(2-methoxyphenyl)methanone (7)
Compound 6 (0.0362 g, 0.114 mmol) and K2CO3 (0.0350 g,
0.25324 mmol) were dissolved in dimethylformamide
(DMF) (1.0 ml) then followed by addition of MeI
(0.0243 g, 0.17122 mmol). This mixture was stirred at
ambient temperature for 1.5 hr then neutralized with 2 N
HCl and diluted with ether and H2O. The organic layer
was separated, dried (MgSO4), and concentrated. The solid
was recrystallized from EtOAc and hexane to afford
4 | CONCLUSIONS
We carefully investigated the iodine-mediated cycliza-
7
(0.0245 g, 0.0740 mmol, EtOAc:Hexane
=
3:10,
tion of chalcones 3/4 and 15/16 in comparison of their
yields. We found that the C2 -OH groups of 3 and 4 are
1
Rf = 0.45) as a white solid. Yield: 65%. Mp 118–119ꢀC. H
NMR (600 MHz, CDCl3) δ 7.81 (s, 1H), 7.56 (d, J = 8.8 Hz,
1H), 7.52 (t, J = 8.1 Hz, 1H), 7.49 (d, J = 9.2 Hz, 1H), 7.48
(d, J = 9.5 Hz, 1H), 7.25 (s, 1H), 7.07 (t, J = 7.4 Hz, 1H),
7.03 (d, J = 8.4 Hz, 1H), 3.8 (s, 3H). 13C NMR (150 MHz,
CDCl3) δ 184.7, 157.7, 154.6, 154.0, 132.9, 131.2, 129.8,
129.1, 127.5, 125.8, 120.5, 116.8, 115.0, 114.1, 111.7, 55.8.
HRMS (ESI) calcd. For C16H12BrO3 [M + H]+ 330.9970.
Found: 330.9970.
0
more efficient than C2-OH groups of 15 and 16 in the
cyclization toward the synthesis of flavones and affords
higher yields. In this regard, the iodine-mediated cycliza-
0
tion of chalcones 5 and 10, which contained both C2 -OH
and C2-OH afforded benzofurans 6 and 11 instead of
expected flavones 8 and 9 in low yields in our present
study.
ACKNOWLEDGMENTS
T.-L. Shih gratefully acknowledges the Ministry of Sci-
ence and Technology of Taiwan (MOST109-2113-M-
032-003) for supporting this work. Anren Hu thanks the
financial support from the Buddhist Tzu-Chi General
Hospital, (TCRD109-77) and the Ministry of Science and
Technology of Taiwan (MOST 108-2113-M-320-001).
3.5 | Benzofuran-2-yl(5-bromo-
2-hydroxyphenyl)methanone (11)
Compound 10 (0.4000 g, 1.250 mmol) was treated with
the same procedure as described in preparation of 6. Puri-
fication by flash column chromatography (EtOAc:Hex-
ane = 1:10–1:8; EtOAc:Hexane = 1:5, Rf = 0.8) afforded
11 (0.0600 g, 0.1410 mmol) as a yellow solid. Yield: 15%.
CONFLICT OF INTEREST
The authors declare no potential conflict of interest.