Helvetica Chimica Acta – Vol. 94 (2011)
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(d-like, J ¼ 6.6, 2 arom. H); 7.53 – 7.50 (m, 3 arom. H); 7.46 – 7.44 (m, 2 arom. H); 7.40 – 7.32 (m, 6 arom.
H); 6.83 (s, 1 H); 6.80 (s, 1 H); 6.11 – 6.05 (m, CH2¼CH); 5.48 (d, J ¼ 16.8, 1 H of CH2¼); 5.38 (d, J ¼
10.8, 1 H of CH2¼); 5.15 (s, PhCH2); 5.06 (s, PhCH2); 4.66 (d, J ¼ 16.8, H2C¼CHCH2OAr).
5,6-Dimethoxy-2-phenyl-7-(prop-2-en-1-yloxy)-4H-1-benzopyran-4-one (7). Compound 6 (1.9 g,
6.1 mmol), K2CO3 (5.1 g, 36.5 mmol), KI (100.0 mg, 0.6 mmol), and MeI (11.2 ml, 18.3 mmol) were
added to dried acetone (150 ml), and the soln. was refluxed at 608 for 8 h. The reaction was monitored by
TLC. The hot soln. was filtered, and the filtrate was evaporated. The crude solid was washed with a small
quantity of cool EtOH and dried under vacuum at 808 for 2 h to give 7 (2.0 g, 96%). White solid. Rf
(AcOEt/hexane 1:2) 0.32. M.p. 138 – 1408. IR (KBr): 3416m, 2939m, 2721w, 1635s, 1606s, 1407s, 1370s,
1295w, 1194w, 1127m, 1009m, 981w, 832m, 812w, 704w. 1H-NMR: 7.87 (dd, J ¼ 7.8, 1.8, 2 arom. H); 7.53 –
7.48 (m, 3 arom. H); 6.81 (s, 1 H); 6.75 (s, 1 H); 6.14 – 6.08 (m, CH2¼CH); 5.50 (dd, J ¼ 17.4, 1.2, 1 H of
CH2¼); 5.38 (dd, J ¼ 10.8, 1.2, 1 H of CH2¼); 4.71 (d, J ¼ 5.4, CH2¼CHCH2OAr); 3.99 (s, MeO); 3.92 (s,
MeO). 13C-NMR ((D6)DMSO): 177.2; 161.1; 156.7; 154.4; 152.7; 140.6; 131.9; 131.6; 131.2; 129.0; 126.0;
118.6; 113.1; 97.4; 69.7; 62.2; 61.5. ESI-MS: 339.2 ([M þ H]þ), 699.2 ([2M þ Na]þ). HR-MS: 339.1228
([M þ H]þ, C20H19Oþ5 ; calc. 339.1227).
5,6-Bis(benzyloxy)-7-hydroxy-2-phenyl-4H-1-benzopyran-4-one (9). To a stirred soln. of 8 (1.3 g,
2.6 mmol) in dry THF (100 ml) was added Pd(PPh3)4 (68.8 mg, 0.06 mmol), and the soln. was stirred.
After ca. 5 min, NaBH4 (151.2 mg, 4.0 mmol) was added. When the reaction was completed (TLC
monitoring), 1m aq. HCl was added until the pH of the soln. was between 4 and 5. The mixture was
concentrated, and the residue was purified by CC (SiO2) to give 9 (0.9 g, 88%). White solid. Rf (AcOEt/
hexane 1:2) 0.54. M.p. 189 – 1918. 1H-NMR: 7.89 – 7.87 (m, 2 arom. H); 7.67 (d-like, J ¼ 6.6, 2 arom. H);
7.53 – 7.50 (m, 3 arom. H); 7.41 (tt, J ¼ 7.2, 1.8, 2 arom. H); 7.37 – 7.35 (m, 4 arom. H); 7.32 – 7.30 (m, 2
arom. H); 6.86 (s, 1 H); 6.70 (s, 1 H); 5.19 (s, ArCH2); 5.17 (s, ArCH2).
7-Hydroxy-5,6-dimethoxy-2-phenyl-4H-1-benzopyran-4-one (10). To a stirred soln. of 7 (338.1 mg,
1.0 mmol) in dry THF (60 ml) was added Pd(PPh3)4 (27.0 mg, 0.02 mmol), and the soln. was stirred. After
ca. 5 min, NaBH4 (60.0 mg, 1.5 mmol) was added. When the reaction was complete (TLC monitoring),
1m aq. HCl was added until the pH of the soln. was between 4 and 5. The mixture was concentrated, and
the residue was purified by CC (SiO2) to give 10 (268.2 mg, 90%). White solid. Rf (AcOEt/hexane 2 :3)
0.17. M.p. 122 – 1248. 1H-NMR: 7.88 – 7.86 (m, 2 arom. H); 7.52 – 7.50 (m, 3 arom. H); 7.00 (s, 1 H); 6.93 (s,
1 H); 4.04 (s, MeO); 4.00 (s, MeO).
5,6-Bis(benzyloxy)-7-(2-hydroxyethoxy)-2-phenyl-4H-1-benzopyran-4-one (16). Compound 9
(930.0 mg, 3.0 mmol), K2CO3 (3.3 g, 24.0 mmol), and 2-bromoethanol (310 ml, 10.0 mmol) were added
to dried acetone (80 ml), and the soln. was refluxed at 608 for 8 h. The reaction was monitored by TLC.
The hot soln. was filtered, and the filtrate was evaporated. The crude solid was washed with a small
quantity of cool EtOH and dried under vacuum at 808 for 2 h to give 16 (1.1 g, 77%). White solid. Rf
(CH2Cl2/MeOH 20 :1) 0.55. M.p. 197 – 1998. IR (KBr): 3384m, 3032m, 2951m, 1633s, 1600s, 1448s, 1361s,
1290w, 1268w, 1191w, 1120m, 1077m, 982w, 833w, 771w, 734w, 697w. 1H-NMR: 7.89 – 7.87 (m, 2 arom. H);
7.67 (dt, J ¼ 6.6, 1.8, 2 arom. H); 7.53 – 7.47 (m, 5 arom. H); 7.40 – 7.34 (m, 6 arom. H); 6.82 (s, 1 H); 6.70
(s, 1 H); 5.15 (s, PhCH2); 5.07 (s, PhCH2); 4.40 – 4.38 (m, 2 H); 3.72 – 3.70 (m, 2 H). 13C-NMR
((D6)DMSO): 175.9; 160.2; 157.3; 154.1; 150.4; 139.1; 137.5; 137.3; 131.6; 130.9; 129.1; 128.4; 128.2; 128.1;
128.0; 127.8; 126.1; 112.4; 107.6; 98.3; 75.8; 74.9; 70.9; 59.4. ESI-MS: 495.2 ([M þ H]þ), 517.3 ([M þ
Na]þ). HR-MS: 495.1806 ([M þ H]þ, C31H27Oþ6 ; calc. 495.1802).
7-(2-Hydroxyethoxy)-5,6-dimethoxy-2-phenyl-4H-1-benzopyran-4-one (11). Compound 10
(149.4 mg, 0.5 mmol), K2CO3 (691.0 mg, 5.0 mmol), and 2-bromoethanol (100.0 ml, 1.5 mmol) were
added to dried acetone (80 ml), and the soln. was refluxed at 608 for 10 h. The reaction was monitored by
TLC. The hot soln. was filtered, and the filtrate was evaporated. The crude solid was washed with a small
quantity of cool EtOH and dried under vacuum at 808 for 2 h to give 11 (128.5 mg, 90%). White solid. Rf
(AcOEt/hexane 2 :1) 0.15. M.p. 115 – 1178. IR (KBr): 3419w, 2938w, 2619w, 1634s, 1601m, 1469m, 1418s,
1361m, 1273w, 1194w, 1120m, 1031w, 994w, 833m, 766w, 704w. 1H-NMR (400 MHz): 7.87 (dd, J ¼ 7.1, 2.0,
2 arom. H); 7.52 – 7.50 (m, 3 arom. H); 6.84 (s, 1 H); 6.67 (s, 1 H); 4.23 (t, J ¼ 4.4, ArOCH2); 4.08 (t, J ¼
4.4, CH2OH); 4.00 (s, MeO); 3.93 (s, MeO). 13C-NMR (100 MHz): 177.2; 161.2; 156.9; 154.4; 152.8;
140.6; 131.5; 131.3; 129.0; 126.0; 113.3; 108.4; 97.5; 70.7; 62.2; 61.6; 61.0. ESI-MS: 343.1 ([M þ H]þ),
707.2 ([2M þ Na]þ). HR-MS: 343.1109 ([M þ H]þ, C19H19Oþ6 ; calc. 343.1176).