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Can. J. Chem. Vol. 91, 2013
bath and DMF (4.6 mL) was added dropwise. In another flask,
2,4,6-trichloro-1,3,5-triazine (TCT) (0.82 g, 4.5 mmol) was added to
DMF (1 mL) and stirred at room temperature for 15 min (TCT
disappearance was monitored by thin-layer chromatography). The
above reaction mixture was then added dropwise to the white
suspension containing TCT/DMF adduct at room temperature for
5 min. After formation of clear solution, the reaction mixture was
heated to 60 °C for 30–40 min and poured into boiling dilute HCl
slowly and cooled. The solution was extracted with ethyl acetate
(30 mL × 2) and the organic layer was dried over anhydrous
Na2SO4. The crude obtained after evaporation of the solvent was
chromatographed over a silica gel column using chloroform–
methanol mixtures as eluent to give isoflavones (9a–9h).
Off-white solid; yield (method A) 760 mg (85%); mp 265–270 °C.
1H NMR (400 MHz, DMSO-d6) ␦: 3.70 (s, 3H), 3.80 (s, 3H), 6.56 (d, J =
8.0 Hz, 1H), 6.63 (s, 1H), 6.86 (s, 1H), 6.93 (d, J = 8.8 Hz, 1H), 7.13 (d,
J = 8.0 Hz, 1H), 7.92 (d, J = 8.8 Hz, 1H), 8.11 (s, 1H), 10.73 (s, 1 H). 13
C
NMR (100 MHz, DMSO-d6) ␦: 55.2, 55.5, 98.6, 102.1, 104.6, 113.5,
114.9, 116.5, 121.5, 127.1, 132.0, 153.8, 157.4, 158.4, 160.6, 162.4, 174.3.
LC–MS: m/z: 297 [M − 1]−. Anal. calcd. for C17H14O5: C 68.45, H 4.73;
found: C 68.46, H 4.75.
Pale brown solid; yield (method A) 594 mg (78%), yield (method
1
B) 670 mg (88%); mp 200–205 °C. H NMR (400 MHz, DMSO-d6) ␦:
6.98 (d, J = 8.8 Hz, 1H), 7.37–7.44 (m, 3H), 7.49 (d, J = 8.8 Hz, 1H),
7.59–7.57 (m, 2H), 8.43 (s, 1H), 9.46 (s, 1H) 10.33 (s, 1H). 13C NMR
(100 MHz, DMSO-d6) ␦: 114.2, 115.6, 117.4, 123.0, 127.5, 128.0, 128.9,
132.2, 132.9, 146.7, 150.1, 153.5, 174.8. LC–MS: m/z: 253 [M − 1]−. Anal.
calcd. for C15H10O4: C 70.86, H 3.96; found: C 70.84, H 4.00.
Method B
A mixture of substituted phenol (3 mmol), phenylacetic acid
(3 mmol), and BF3·Et2O (9 mmol) was stirred to 80–90 °C for
90 min under N2. The mixture was then poured into NaOAc solu-
tion (100 mL, 10%) and allowed to stand for 4 h and the solution
extracted with EtOAc (3 × 100 mL). the combined organic layer was
washed with water (20 mL) and brine (20 mL) and dried over
anhydrous Na2SO4. The crude obtained after evaporation of the
solvent was chromatographed over a silica gel column using
hexane–EtOAc mixtures as eluent to give deoxybenzoins (7f–7h).
The purified materials were then used for the synthesis of isofla-
vones. A mixture of deoxybenzoin (3 mmol) and BF3·Et2O
(7.5 mmol) was cooled to 10 °C and DMF (4.6 mL) was added drop-
wise. The cyclization procedure and workup are similar to
method A.
Brown solid; yield (method A) 640 mg (75%), yield (method B) 725
mg (85%); mp 216–218 °C. 1H NMR, (400 MHz, DMSO-d6) ␦: 3.78 (s,
3H), 6.94 (d, J = 7.6 Hz, 1H), 6.97 (d, J = 8.8 Hz, 1H), 7.14–7.17 (m,
2H), 7.33 (t, J = 7.6 Hz, 1H), 7.49 (d, J = 8.8 Hz, 1H), 8.44 (s, 1H), 9.41
(s, 1H), 10.32 (s, 1H). 13C NMR (100 MHz, DMSO-d6) ␦: 55.0, 113.1,
114.2, 114.7, 115.7, 117.4, 121.2, 122.7, 129.0, 132.9, 133.5, 146.6, 150.1,
153.6, 158.9, 174.7. LC–MS: m/z: 283 [M − 1]−. Anal. calcd. for
C16H12O5: C 67.60, H 4.25; found: C 67.58, H 4.28.
Off-white solid; yield (method A) 621 mg (87%); mp 210–213 °C.
1H NMR (400 MHz, DMSO-d6) ␦: 6.88 (d, J = 2.4 Hz, 1H), 6.96 (dd, J =
2.4, 8.4 Hz, 1H), 7.34–7.44 (m, 3H), 7.57 (d, J = 7.2 Hz, 2H), 7.99 (d, J =
8.8 Hz,1H), 8.36 (s, 1H), 10.80 (s, 1H). 13C NMR (100 MHz, DMSO-d6) ␦:
102.1, 115.2, 116.6, 123.5, 127.2, 127.6, 128.0, 128.8, 132.1, 153.6, 157.4,
162.6, 174.3. LC–MS: m/z: 237 [M − 1]−. Anal. calcd. for C15H10O3: C
75.62, H 4.23; found: C 75.60, H 4.27.
Pale brown solid; yield (method A) 640 mg (75%), yield (method
1
B) 760 mg (89%); mp 252–254 °C. H NMR (400 MHz, DMSO-d6) ␦:
3.79 (s, 3H), 6.96 (d, J = 8.8 Hz, 1H), 6.99 (d, J = 8.8 Hz, 2H), 7.48 (d,
J = 8.8 Hz, 1H), 7.52 (d, J = 8.8 Hz, 2H), 8.38 (s, 1H), 9.42 (s, 1H), 10.29
(s, 1H). 13C NMR (100 MHz, DMSO-d6) ␦: 55.1, 113.5, 114.1, 115.6, 117.4,
122.6, 124.4, 130.0, 132.8, 146.7, 149.8, 150.0, 152.8, 158.9, 175.0.
LC–MS: m/z: 283 [M − 1]−. Anal. calcd. for C16H12O5: C 67.60, H 4.25;
found: C 67.59, H 4.28.
7-Hydroxy-3-(3-methoxyphenyl)-4H-chromen-4-one (9b) (Table 2,
entry 2)
Pale pink solid; yield (method A) 715 mg (89%); mp 215–217 °C. 1H
NMR (400 MHz, DMSO-d6) ␦: 3.78 (s, 3H), 6.88 (s, 1H), 6.93–6.96 (m,
2H), 7.13–7.15 (m, 2H), 7.33 (t, J = 8.0 Hz, 1H), 7.98 (d, J = 8.8 Hz, 1H),
8.38 (s, 1H), 10.79 (s, 1H). 13C NMR (100 MHz, DMSO-d6) ␦: 55.06,
102.1, 113.2, 114.6, 115.2, 116.6, 121.1, 123.3, 127.2, 129.0, 133.4, 153.8,
157.3, 159.0, 162.6, 174.3. LC–MS: m/z: 267 [M − 1]−. Anal. calcd. for
C16H12O4: C 71.64, H 4.51; found: C 71.60, H 4.56.
General experimental procedure for homo-isoflavones
(10a–10f)
Method A
A mixture of substituted phenol (3 mmol), 3-phenylpropanoic
acid (3 mmol), and BF3·Et2O (15 mmol) was heated to 90 °C for
90 min under N2. The reaction mixture was then cooled to 10 °C
and DMF (4.6 mL) was added dropwise. In another flask, 2,4,6-
trichloro-1,3,5-triazine (TCT) (0.82 g, 4.5 mmol) was added to DMF
(1 mL) and stirred at room temperature for 15 min (TCT disappear-
ance was monitored by thin-layer chromatography). The above
reaction mixture was then added dropwise to the white suspen-
sion containing TCT/DMF adduct at room temperature for 5 min.
After formation of clear solution, the reaction mixture was heated
to 60 °C for 30–40 min and poured into boiling dilute HCl slowly
and cooled. The solution was extracted with ethyl acetate (30 mL ×
2) and the organic layer was dried over anhydrous Na2SO4. The
crude obtained after evaporation of the solvent was chromato-
graphed over a silica gel column using chloroform–methanol mix-
tures as eluent to give isoflavones (10a–10h).
7-Hydroxy-3-(4-methoxyphenyl)-4H-chromen-4-one27 (9c) (Table 2,
entry 3)
Off-white solid; yield (method A) 723 mg (90%); mp 257–258 °C.
1H NMR, (400 MHz, DMSO-d6) ␦: 3.78 (s, 3H), 6.88 (d, J = 2 Hz, 1H),
6.94 (dd, J = 2.4, 8.8 Hz, 1H), 6.98 (d, J = 8.8 Hz, 2H), 7.49 (d, J = 8.8 Hz,
2H), 6.97 (d, J = 8.8 Hz, 1H), 8.31 (s, 1H). 13C NMR (100 MHz, DMSO-d6)
␦: 55.1, 102.0, 113.6, 114.1, 115.0, 116.6, 123.1, 124.1, 127.2, 130.0, 153.0,
157.4, 158.9, 162.3, 174.6. LC–MS: m/z: 267 [M − 1]−. Anal. calcd. for
C16H12O4: C 71.64, H 4.51; found: C 71.60, H 4.55.
7-Hydroxy-3-(4-hydroxyphenyl)-4H-chromen-4-one28 (9d) (Table 2,
entry 4)
Pale brown powder; yield (method A) 670 mg (88%); mp 310–
312 °C. 1H NMR (400 MHz, DMSO-d6) ␦: 6.79 (d, J = 8.4, 2H), 6.83 (d,
J = 2.0 Hz, 1H), 6.91 (dd, J = 2.0, 8.0 Hz, 1H), 7.36 (d, J = 8.4 Hz, 2 H),
7.96 (d, J = 8.0 Hz, 1H), 8.28 (s, 1H), 9.55 (s, 1H), 10.83 (s, 1H). 13C NMR
(100 MHz, DMSO-d6) ␦: 102.0, 114.9, 115.1, 122.5, 123.5, 127.2, 130.0,
157.2, 157.3, 162.4, 174.7. LC–MS: m/z: 253 [M − 1]−. Anal. calcd. for
C15H10O4: C 70.86, H 3.96; found: C 70.85, H 3.98.
Method B
A mixture of substituted phenol (3 mmol), 3-phenylpropanoic
acid (3 mmol), and BF3·Et2O (9 mmol) was stirred to 80–90 °C for
90 min under N2. The mixture was then poured into NaOAc solu-
tion (100 mL, 10%) and allowed to stand for 4 h and the solution
extracted with EtOAc (3 × 100 mL). The combined organic layer
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