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3-H), 2.72 (dd, J ¼ 3.2, 13.6 Hz, 1H, 3-H); 13C NMR (100 MHz, acetate, 40 : 60) to obtain methyl 7-hydroxy-2-(substituted phenyl)-4-
DMSO-d6): d 189.09, 169.48, 164.51, 163.48, 138.28, 136.50, oxo-4H-chromene-5-carboxylates 6(a–f) in 60% yield.
133.64, 131.72, 129.91, 129.09, 129.09, 110.87, 110.02, 104.28,
4.3.12 Methyl
7-hydroxy-2-(4-methoxyphenyl)-4-oxo-4H-
78.69, 52.86, 43.63; LCMS (ESI): m/z calculated for C17H13ClO5: chromene-5-carboxylate (6a). Mp: 226–228 C; IR (KBr, cmꢀ1):
332.73, found: 333.0. Elemental analysis: calculated for 3446 (OH), 1735 (C]O), 1624 (C]O); 1H NMR (400 MHz,
ꢁ
C
17H13ClO5: C, 61.36, H, 3.93; found: C, 61.30, H, 3.87.
4.3.8 Methyl 2-(4-bromophenyl)-7-hydroxy-4-oxo-3,4-dihy- H), 7.12 (d, J ¼ 7.2 Hz, 2H, 30-H, 50-H), 7.10 (d, J ¼ 2 Hz, 1H, 6-H),
DMSO-d6): d 11.14 (s, 1H, OH), 8.04 (d, J ¼ 7.2 Hz, 2H, 20-H, 60-
dro-2H-chromene-5-carboxylate (5d). Yellow solid (40%), Rf 0.67 6.82 (d, J ¼ 1.6 Hz, 1H, 8-H), 6.79 (s, 1H, 3-H), 3.86 (s, 3H, OCH3),
(EtOAc/hexane, 3 : 7); mp: 208 ꢁC; IR (KBr, cmꢀ1): 3361 (OH), 3.81 (s, 3H, OCH3); 13C NMR (100 MHz, DMSO-d6): d 175.68,
1735 (C]O); 1H NMR (400 MHz, DMSO-d6): d 10.97 (s, 1H, OH), 169.19, 162.54, 162.39, 158.55, 157.70, 134.55, 128.59, 127.11,
7.60 (d, J ¼ 8.8 Hz, 2H, 30-H, 50-H), 7.46 (d, J ¼ 8.4 Hz, 2H, 20-H, 123.49, 114.98, 114.81, 113.94, 113.55, 105.58, 104.25, 55.97,
60-H), 6.44 (s, 1H, 8-H), 6.41 (s, 1H, 6-H), 5.62 (dd, J ¼ 2.4, 52.86; LCMS (ESI): m/z calculated for C18H14O6: 326.3, found:
12.8 Hz, 1H, 2-H), 3.74 (s, 3H, OCH3), 3.08 (q, J ¼ 4.4, 12.8 Hz, 327.0. Elemental analysis: calculated for C18H14O6: C, 66.25, H,
1H, 3-H), 2.72 (dd, J ¼ 2.8, 14.4 Hz, 1H, 3-H); 13C NMR (100 4.32; found: C, 66.31, H, 4.28.
MHz, DMSO-d6): d 189.05, 169.48, 164.53, 163.46, 138.69,
4.3.13 Methyl
2-(3,4-dimethoxyphenyl)-7-hydroxy-4-oxo-
136.50, 132.01, 132.01, 129.34, 129.34, 122.23, 110.87, 110.03, 4H-chromene-5-carboxylate (6b). Mp: 233–236 ꢁC; IR
104.28, 78.72, 52.86, 43.59; LCMS (ESI): m/z calculated for (KBr, cmꢀ1): 3444 (OH), 1737 (C]O), 1627 (C]O); 1H NMR (400
C
17H13BrO5: 377.18, found: 377.8. Elemental analysis: calcu- MHz, DMSO-d6): d 11.08 (s, 1H, OH), 7.63 (d, J ¼ 8 Hz, 1H, 60-H),
lated for C17H13BrO5: C, 54.13, H, 3.47; found: C, 54.08, H, 3.43. 7.52 (s, 1H, 20-H), 7.13 (m, 2H, 50-H, 6-H), 6.84 (s, 1H, 8-H), 6.79
4.3.9 Methyl 7-hydroxy-2-(4-methylphenyl)-4-oxo-3,4-dihy- (s, 1H, 3-H), 3.85 (s, 3H, OCH3), 3.81 (s, 3H, OCH3), 3.78 (s, 3H,
dro-2H-chromene-5-carboxylate (5e). Yellow solid (40%), Rf 0.7 OCH3); 13C NMR (100 MHz, DMSO-d6): d 175.74, 169.19, 162.48,
(EtOAc/hexane, 3.5 : 6.5); mp: 198 ꢁC; IR (KBr, cmꢀ1): 3367 (OH), 162.36, 157.74, 152.34, 149.47, 134.51, 123.59, 120.29, 113.53,
1739 (C]O); 1H NMR (400 MHz, DMSO-d6): d 10.97 (s, 1H, OH), 113.39, 112.14, 109.83, 105.89, 104.34, 56.32, 56.17, 52.87;
7.40 (d, J ¼ 8 Hz, 2H, 20-H, 60-H), 7.23 (d, J ¼ 7.6 Hz, 2H, 30-H, 50- LCMS (ESI): m/z calculated for C19H16O7: 356.32, found: 357.0.
H), 6.45 (s, 1H, 8-H), 6.43 (s, 1H, 6-H), 5.58 (dd, J ¼ 2.4, 12.4 Hz, Elemental analysis: calculated for C19H16O7: C, 64.04, H, 4.52;
1H, 2-H), 3.77 (s, 3H, OCH3), 3.13 (q, J ¼ 4.4, 12.8 Hz, 1H, 3-H), found: C, 64.16, H, 4.59.
2.71 (dd, J ¼ 2.4, 14.8 Hz, 1H, 3-H), 2.32 (s, 3H, CH3); 13C NMR
4.3.14 Methyl
2-(4-chlorophenyl)-7-hydroxy-4-oxo-4H-
(100 MHz, DMSO-d6): d 189.34, 169.48, 164.38, 163.59, 138.39, chromene-5-carboxylate (6c). Mp: 262–268 C; IR (KBr, cmꢀ1):
136.42, 136.21, 129.51, 129.51, 127.10, 127.10, 110.84, 109.80, 3645 (OH), 1714 (C]O), 1697 (C]O); 1H NMR (400 MHz,
104.19, 79.30, 52.78, 43.62, 21.24; LCMS (ESI): m/z calculated for DMSO-d6): d 11.19 (s, 1H, OH), 8.07 (d, J ¼ 8.8 Hz, 2H, 30-H, 50-
ꢁ
C
18H16O5: 312.31, found: 313.05. Elemental analysis: calculated H), 7.60 (d, J ¼ 8.4 Hz, 2H, 20-H, 60-H), 7.08 (s, 1H, 6-H), 6.89 (s,
for C18H16O5: C, 69.21, H, 5.15; found: C, 69.27, H, 5.21.
1H, 8-H), 6.80 (s, 1H, 3-H), 3.78 (s, 3H, OCH3); 13C NMR (100
4.3.10 Methyl 2-(2-uorophenyl)-7-hydroxy-4-oxo-3,4-dihy- MHz, DMSO-d6): d 175.75, 169.06, 162.63, 161.24, 157.79,
dro-2H-chromene-5-carboxylate (5f). Yellow solid (40%), Rf 0.68 136.99, 134.60, 130.28, 129.62, 129.62, 128.60, 128.60, 113.86,
(EtOAc/hexane, 3 : 7); mp: 195 ꢁC; IR (KBr, cmꢀ1): 3461 (OH), 113.36, 107.48, 104.32, 52.91; LCMS (ESI): m/z calculated for
1735 (C]O); 1H NMR (400 MHz, DMSO-d6): d 11.03 (s, 1H, OH),
C17H11ClO5: 330.71, found 331.0. Elemental analysis: calculated
7.64–7.68 (m, 1H, 30-H), 7.45–7.48 (m, 1H, 40-H), 7.26–7.32 (m, for C17H11ClO5: C, 61.73, H, 3.34; found: C, 61.67, H, 3.28.
2H, 50-H, 60-H), 6.46 (s, 2H, 6-H, 8-H), 5.85 (dd, J ¼ 2.4, 13.2 Hz,
4.3.15 Methyl 2-(4-bromophenyl)-7-hydroxy-4-oxo-4H-
1H, 2-H), 3.78 (s, 3H, OCH3), 3.23 (q, J ¼ 3.2, 14 Hz, 1H, 3-H), chromene-5-carboxylate (6d). Mp: 275–277 ꢁC; IR
2.73 (dd, J ¼ 2.4, 14 Hz, 1H, 3-H); 13C NMR (100 MHz, DMSO-d6): (KBr, cmꢀ1): 3564 (OH), 1737 (C]O), 1627 (C]O); 1H NMR (400
d 188.85, 169.40, 164.46, 163.43, 161.32, 158.86, 136.50, 131.40, MHz, DMSO-d6): d 11.18 (s, 1H, OH), 8.0 (d, J ¼ 8 Hz, 2H, 30-H,
128.97, 125.90, 125.24, 116.32, 110.70, 104.15, 73.95, 52.82, 50-H), 7.75 (d, J ¼ 8 Hz, 2H, 20-H, 60-H), 7.07 (s, 1H, 3-H), 6.90 (s,
42.27; LCMS (ESI): m/z calculated for C17H13FO5: 316.28, found: 1H, 6-H), 6.81 (s, 1H, 8-H), 3.78 (s, 3H, OCH3); 13C NMR (100
317.05. Elemental analysis: calculated for C17H13FO5: C, 64.55, MHz, DMSO-d6): d 175.90, 169.90, 162.70, 161.52, 157.84,
H, 4.13; found: C, 64.49, H, 4.20.
4.3.11 General procedure for the synthesis of methyl 7- 113.35, 107.41, 104.38, 53.03; LCMS (ESI): m/z calculated for
hydroxy-2-(substituted phenyl)-4-oxo-4H-chromene-5-carboxylates 17H11BrO5: 375.17, found: 376.9, 378.9. Elemental analysis:
134.62, 132.62, 132.62, 130.59, 128.76, 128.76, 126.01, 113.93,
C
(6a–f). I2 (0.15 mmol) was added to methyl 7-hydroxy-2- calculated for C17H11BrO5: C, 54.42, H, 2.95; found: C, 54.48, H,
(substituted phenyl)-4-oxo-3,4-dihydro-2H-chromene-5-carboxylates 2.95.
(5a–f) (3 mmol) in DMSO (10 mL), and the mixture was reuxed
4.3.16 Methyl
7-hydroxy-2-(4-methylphenyl)-4-oxo-4H-
for 1 h. The progress of the reaction was observed by TLC. Aer chromene-5-carboxylate (6e). Mp: 240–242 ꢁC; IR (KBr, cmꢀ1):
completion, the reaction mixture was cooled to room temperature 3516 (OH), 1737 (C]O), 1627 (C]O); 1H NMR (400 MHz,
and quenched with water. The aqueous layer was extracted with DMSO-d6): d 11.18 (s, 1H, OH), 7.95 (d, J ¼ 8.0 Hz, 2H, 20-H, 60-
ethyl acetate. The organic layer was separated, dried over sodium H), 7.38 (d, J ¼ 8.0 Hz, 2H, 30-H, 50-H), 7.10 (s, 1H, 6-H), 6.84
sulfate and concentrated, and the crude product was obtained, (s, 1H, 8-H), 6.83 (s, 1H, 3-H), 3.81 (s, 3H, OCH3), 2.39 (s, 3H,
which was puried by column chromatography (hexane–ethyl CH3); 13C NMR (100 MHz, DMSO-d6): d 175.76, 169.14,
162.49, 157.78, 142.42, 134.58, 130.25, 130.14, 130.14, 128.55,
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RSC Adv., 2018, 8, 10634–10643 | 10641