P. Nealmongkol et al. / Tetrahedron 69 (2013) 9277e9283
9281
CDCl3):
1H), 7.56e7.10 (m, 4H).
d
7.96 (d, J¼7.8 Hz, 1H), 7.60e7.52 (m, 2H), 7.46 (t, J¼7.5 Hz,
by flash column chromatography (Hexane 100%) to obtain product
as pink oil (57 mg, 35%): Rf 0.51 (20% EtOAc/Hexane). IR (UATR):
nmax 2975, 1578, 1460, 1283, 1223, 1032, 840 cmꢃ1 1H NMR
.
4.3.4. 7-Methylchromeno[3,4-b]indol-6(7H)-one (24a). White solid
(2 mg, 45%): Rf 0.40 (20% EtOAc/Hexane). Mp: 170 ꢀC. IR (UATR):
(300 MHz, CDCl3):
d
7.69 (d, J¼8.7 Hz, 1H), 7.20 (d, J¼2.4 Hz, 1H),
6.60 (dd, J¼8.7, 2.1 Hz, 1H), 3.78 (s, 3H); 13C NMR (75 MHz, CDCl3):
nmax 2960, 2913, 2850, 1705, 1467, 1259, 1016, 730 cmꢃ1
.
1H NMR
d 160.1, 140.1, 129.8, 118.3, 115.3, 89.4, 55.5. EI-MS: m/z (%) 312
(300 MHz, CDCl3):
d
8.32e8.25 (m, 2H), 7.58e7.41 (m, 6H), 4.28 (s,
156.2, 152.2, 150.8, 141.2, 127.3,
(MþHþ, 87), 297 (17), 172 (30), 63 (100). TOF-HRMS calcd for
3H). 13C NMR (75 MHz, CDCl3):
d
C7H6BrIO: 311.8641; found 311.8645, 313.8622.
127.2, 124.5, 123.2, 122.8, 121.8, 121.3, 121.0, 118.9, 117.1, 111.0, 31.5.
EI-MS: m/z (%) 250 (MþHþ, 17), 249 (Mþ, 100), 248 (55), 165 (12),
149 (12), 86 (24). HRMS (microTOF): m/z calcd for C16H12NO2
(MþHþ) 250.0866; found 250.0862. Chromeno[3,4-b]indol-6(7H)-
one (24b). Brown solid (0.4 mg, 11%): Rf 0.46 (40% EtOAc/Hexane).
4.5. General procedure for the preparation of biarylcarbox-
aldehydes (28aec)
The mixture of 2-formylphenyl boronic acid 26aec (1.0 equiv),
2-bromo-1-iodo-4-methoxybenzene 27 (2.0 equiv), and 5 mol %
PdCl2(PPh3)2 in THF (5 mL) was stirred under Ar atmosphere at
room temperature. A solution of 2 N K2CO3 (25 mL) was then
transferred into the reaction via syringe until the reaction turned
a brown-red solution. The reaction was allowed to stir at room
temperature overnight. After checking by TLC, the reaction was
quenched with water and partitioned with EtOAc to obtain the
dark-brown crude oil. The crude product was purified by flash
chromatography or preparative thin layer chromatography (EtOAc/
Hexane) to obtain the product.
1H NMR (300 MHz, CDCl3):
d
7.94 (d, J¼7.8 Hz, 1H), 7.67 (dd, J¼7.5,
1.2 Hz, 1H), 7.47e7.38 (m, 2H), 7.31e7.21 (m, 4H).
4.3.5. 4H-Furo[3,2-c]chromen-4-one (25). Brown solid (20 mg,
30%): Rf 0.14 (10% EtOAc/Hexane). Mp: 171 ꢀC. IR (UATR): nmax 1686,
1483, 1313, 1146, 753 cmꢃ1 1H NMR (300 MHz, CDCl3):
. d 7.50 (d,
J¼1.5 Hz, 1H), 7.48e7.29 (m, 4H), 6.87 (d, J¼1.5 Hz, 1H). 13C NMR
(75 MHz, CDCl3):
d 167.8, 156.3, 142.5, 134.3, 132.1, 130.9, 129.7,
129.2, 128.1, 126.2, 111.6. EI-MS: m/z (%): 187 (MþHþ, 100), 170 (2),
149 (6), 131 (5), 115 (14). TOF-HRMS calcd for C11H7O3: 187.0389;
found 187.0385.
4.5.1. 20-Bromo-4,40-dimethoxy-[1,10-biphenyl]-2-carbaldehyde
(28a). Yellow solid (32 mg, 62%): Rf 0.40 (5% EtOAc/Hexane). Mp:
104 ꢀC. IR (UATR): nmax 2916, 2848, 2344, 1688, 1601, 1481 cmꢃ1. 1H
4.3.6. 3,8-Dimethoxy-6H-benzo[c]chromen-6-one
(30a). Yellow
solid (37 mg, 61%). Rf 0.43 (50% CH2Cl2/Hexane). Mp: 124 ꢀC. IR
(UATR): nmax 2924, 2846, 1732, 1623, 1491, 1319, 1295 cmꢃ1. 1H NMR
NMR (400 MHz, CDCl3):
7.25e7.19 (m, 4H), 6.94 (dd, J¼8.4, 2.5 Hz, 1H), 3.90 (s, 3H), 3.86 (s,
3H). 13C NMR (100 MHz, CDCl3):
191.5, 159.9, 159.4, 137.3, 134.9,
d
9.75 (s, 1H), 7.50 (d, J¼2.5 Hz, 1H),
(300 MHz, CDCl3):
d
7.90 (d, J¼9.0 Hz, 1H), 7.85 (d, J¼8.7 Hz, 1H),
7.75 (d, J¼2.7 Hz, 1H), 7.36 (dd, J¼8.8, 3.0 Hz, 1H), 6.90 (dd, J¼9.0,
d
2.5 Hz, 1H), 6.85 (d, J¼2.4 Hz, 1H), 3.92 (s, 3H), 3.87 (s, 3H). 13C NMR
132.4, 132.3, 130.5, 124.6, 121.0, 117.8, 113.4, 109.7, 55.6, 55.5. EI-MS:
m/z (%) 230 (Mþ, 1), 241 (100), 198 (28), 121 (14). TOF-HRMS calcd
for C15H14BrO3: 321.0120; found 321.0132, 323.0117.
(75 MHz, CDCl3):
d 161.5, 160.6, 159.0, 151.5, 128.5, 124.3, 123.1,
122.7, 120.9, 112.3, 111.2, 110.9, 101.4, 55.6 (2C). EI-MS: m/z (%) 256
(Mþ, 23), 241 (15), 178 (20), 149 (16). TOF-HRMS calcd for C15H13O4:
257.0808; found 257.0811.
4.5.2. 20-Bromo-40-methoxy-[1,10-biphenyl]-2-carbaldehyde
(28b). Pink oil (20 mg, 43%): Rf 0.26 (5% EtOAc/Hexane). IR (UATR):
4.3.7. 3-Methoxy-6H-benzo[c]chromen-6-one (30b). Yellow solid
(3 mg, 36%): Rf 0.46 (10% EtOAc/Hexane). Mp: 107 ꢀC. IR (UATR):
nmax 2838, 2933, 1693, 1597, 1221, 1033, 776 cmꢃ1 1H NMR
.
(400 MHz, CDCl3):
d
9.81 (s, 1H), 8.02 (dd, J¼7.7, 1.1 Hz, 1H), 7.64 (td,
nmax 2924, 2846, 1732, 1623, 1491, 1319, 1295 cmꢃ1
.
1H NMR
J¼7.5, 1.4 Hz, 1H), 7.52 (t, J¼7.6 Hz, 1H), 7.32 (dd, J¼7.5, 0.6 Hz, 1H),
(300 MHz, CDCl3):
d
8.36 (d, J¼8.1 Hz, 1H), 8.01 (d, J¼8.4 Hz, 1H),
7.24 (d, J¼1.0 Hz, 1H), 7.22 (m, 1H), 6.96 (dd, J¼8.4, 2.5 Hz, 1H), 3.86
7.95 (d, J¼8.1 Hz, 1H), 7.79 (t, J¼7.8 Hz, 1H), 7.51 (t, J¼8.1 Hz, 1H),
(s, 3H). 13C NMR (100 MHz, CDCl3):
d 191.6,160.0,144.2, 133.9,133.4,
6.92 (d, J¼8.7 Hz, 1H), 6.88 (s, 1H), 3.89 (s, 3H). 13C NMR (75 MHz,
132.0, 131.2, 130.8, 128.2, 126.9, 124.0, 117.8, 113.5, 55.6. EI-MS: m/z
(%) 290 (Mþ, 0.35), 211 (100), 196 (11), 168 (25), 139 (30), 105 (6).
TOF-HRMS calcd for C14H12BrO2: 291.0015; found 291.0022,
293.0000.
CDCl3):
d 161.5, 135.1, 134.8, 130.5, 127.7, 124.4, 123.9, 123.7, 121.0,
119.1, 112.4, 111.1, 101.6, 55.6. EI-MS: m/z (%) 256 (Mþ, 23), 241 (14),
178 (20), 149 (16). TOF-HRMS calcd for C14H9O3: 213.0546; found
213.0554.
4.5.3. 6-(2-Bromo-4-methoxyphenyl)benzo[d][1,3]dioxole-5-
carbaldehyde (28c). Brown oil (38 mg, 71%): Rf 0.37 (5% EtOAc/
Hexane). IR (UATR): nmax 2909, 2849, 1680, 1602, 1476, 1235,
4.3.8. 3-Methoxy-6H-[1,3]dioxolo[40,50:4,5]benzo[1,2-c]chromen-6-
one (30c). Brown solid (2 mg, 29%): Rf 0.43 (50% CH2Cl2/Hexane).
Mp: 118 ꢀC. IR (UATR): nmax 2921, 2849, 2155, 1716, 1612, 1480, 1270,
1034 cmꢃ1. 1H NMR (400 MHz, CDCl3):
d
9.55 (s, 1H), 7.44 (s, 1H),
7.21 (d, J¼2.4 Hz, 1H), 7.19 (d, J¼8.8 Hz, 1H), 6.92 (dd, J¼8.6, 2.4 Hz,
1H), 6.20 (s, 2H), 3.85 (s, 3H). 13C NMR (100 MHz, CDCl3):
189.9,
1034, 935 cmꢃ1. 1H NMR (300 MHz, DMSO-d6):
d
8.19 (d, J¼8.4 Hz,
1H), 7.91 (s, 1H), 7.53 (s, 1H), 6.99e6.95 (m, 2H), 6.24 (s, 2H), 3.84 (s,
3H). 13C NMR (75 MHz, DMSO-d6):
161.2, 154.6, 151.9, 148.3, 132.9,
d
d
160.0, 151.9, 141.6, 132.2, 130.4, 124.3, 117.9, 114.4, 113.4, 110.7, 110.6,
105.9, 102.0, 55.6. EI-MS: m/z (%) 334 (MþHþ, 1), 255 (100), 212
(23), 197 (10), 154 (10). TOF-HRMS calcd for C15H12BrO4: 334.9913;
found 334.9911, 336.9891.
130.0, 125.0, 113.4, 112.7, 111.9, 107.4, 103.0, 101.6, 101.5, 56.2 EI-MS:
m/z (%) 271 (MþHþ, 100), 256 (53), 241 (29), 128 (12). TOF-HRMS
calcd for C15H11O5: 271.0610; found 271.0603.
4.4. General procedure for the preparation of 2-bromo-1-
iodo-4-methoxybenzene (27)
4.6. General procedure for the preparation of biaryl esters
(29aec)
A
mixture of 3-bromophenol (0.53 mmol, 1.0 equiv), I2
To
a
solution of 20-bromo-40-methoxy-(1,10-biphenyl)-2-
(0.53 mmol, 1.0 equiv), and CF3COOAg (0.80 mmol, 1.5 equiv) in
CHCl3 (5 mL) was stirred under Ar atmosphere for 3 h. The reaction
was quenched with saturated Na2S2O3 (50 mL) and extracted with
CH2Cl2 (3ꢂ25 mL). The solvent was then removed by rotary evap-
oration to give the brown crude oil. The crude product was purified
carbaldehydes 28aec (1.0 equiv), pyridine (5 mL) in water
(15 mL) was added KMnO4 (2.0 equiv) at ambient atmosphere. The
reaction was then refluxed and monitored by TLC until the starting
material was completely oxidized. The reaction was cooled to room
temperature and acidified with 2 N HCl to afford a white