The Journal of Organic Chemistry
Article
2-((3aR,5R,6S,6aR)-6-Ethoxy-2,2-dimethyltetrahydrofuro[2,3-d]-
[1,3]dioxol-5-yl)naphthalene-1,4-dione (7c). Compound 7c was
prepared using (3aR,5R,6S,6aR)-6-ethoxy-2,2-dimethyl-5-((E)-2-
nitrovinyl)tetrahydrofuro[2,3-d][1,3]dioxole (6c) as a starting ma-
terial to give the product as a yellow thick liquid: 56% yield (193 mg);
1316, 1286, 1216, 1146, 1035, 1010, 855, 758; HRMS (ESI) m/z
calcd for C15H12BrO2[M + H]+ 303.0021, found 303.0022 (one of the
major peaks).
8-Bromo-6-chloro-3-phenylchroman-4-one (9d). Compound 9d
was prepared using 3-bromo-5-chlorosalicylaldehyde (8d) and β-
nitrostyrene (3a) as starting materials to give the product as a yellow
[α]2D5 −22.8 (c 0.30, CHCl3); H NMR (300 MHz, CDCl3) δ 1.09−
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1.17 (m, 5H), 1.39 (s, 3H), 3.91−3.99 (m, 1H), 4.05−4.12 (m, 1H),
4.54−4.66 (m, 3H), 5.86 (d, J = 3.1 Hz, 1H), 6.98 (s, 1H), 7.68−7.72
(m, 2H), 8.07−8.10 (m, 2H); 13C NMR (75 MHz, CDCl3) δ 15.8,
25.9, 26.4, 66.5, 79.5, 81.2, 83.8, 111.1, 122.7, 127.5, 130.7, 132.2,
133.4, 134.2, 135.3, 136.5, 146.6, 186.9, 187.6; FTIR (neat, cm−1)
3022, 2926, 2830, 1670, 1563, 1427, 1356, 1292, 1208, 1158; HRMS
(ESI) m/z calcd for C19H21O6 [M + H]+ 345.1338, found 345.1340.
(R)-2-(2,2-Dimethyl-1,3-dioxolan-4-yl)naphthalene-1,4-dione
(7d). Compound 7d was prepared using (R,E)-2,2-dimethyl-4-(2-
nitrovinyl)-1,3-dioxolane (6d) as a starting material to give the
product as a yellow thick liquid: 64% yield (165 mg); [α]2D5 −32.6 (c
solid: 74% yield (247 mg); mp 112−114 °C; H NMR (300 MHz,
CDCl3) δ 3.92−3.99 (m, 1H), 4.68−4.76 (m, 2H), 7.17−7.20 (m,
2H), 7.23−7.34 (m, 3H), 7.67 (d, J = 2.4 Hz, 1H), 7.81 (d, J = 2.4
Hz, 1H); 13C NMR (75 MHz, CDCl3) δ 51.5, 71.9, 112.3, 122.3,
126.4, 127.2, 128.1, 128.5, 129.0, 133.7, 138.5, 156.5, 190.2; FTIR
(KBr, cm−1) 3052, 2877, 1686, 1592, 1471, 1313, 1284, 1218, 1144,
1036, 1015, 857, 768, 622; HRMS (ESI) m/z [M + H]+ calcd for
C15H11BrClO2 336.9631, found 336.9632 (one of the major peaks).
6,8-Dichloro-3-phenylchroman-4-one (9e). Compound 9e was
prepared using 3,5-dichlorosalicylaldehyde (8e) and β-nitrostyrene
(3a) as starting materials to give the product as a yellow thick liquid:
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0.30, CHCl3); H NMR (300 MHz, CDCl3) δ 1.21 (s, 3H), 1.36 (s,
76% yield (221 mg); H NMR (300 MHz, CDCl3) δ 4.01−4.06 (m,
3H), 3.82−4.12 (m, 2H), 4.30−4.34 (m, 1H), 7.06 (s, 1H), 7.87−
7.91 (m, 2H), 8.15−8.19 (m, 2H); 13C NMR (75 MHz, CDCl3) δ
26.3, 27.3, 74.9, 82.6, 111.1, 120.9, 129.1, 130.9, 132.1, 133.3, 134.3,
135.3, 136.4, 148.8, 185.4, 186.4; FTIR (neat, cm−1) 3052, 2926,
2830, 1668, 1563, 1432, 1356, 1292, 1224, 1162; HRMS (ESI) m/z
calcd for C15H15O4[M + H]+ 259.0970, found 259.0972.
1H), 4.75−4.79 (m, 2H), 7.24−7.27 (m, 2H), 7.30−7.41 (m, 3H),
7.56−7.58 (m, 1H), 7.82−7.84 (m, 1H); 13C NMR (75 MHz,
CDCl3) δ 51.6, 71.9, 122.4, 123.7, 125.7, 126.8, 128.1, 128.4, 128.6,
129.0, 133.7, 135.5, 155.7, 190.2; FTIR (neat, cm−1) 3082, 2906,
2867, 1684, 1572, 1473, 1315, 1287, 1228, 1025, 662, 585; HRMS
(ESI) m/z calcd for C15H11Cl2O2 [M + H]+ 293.0136, found
293.0135 (one of the major peaks).
General Procedure for the Synthesis of Isoflavanone (9a−
k). Salicylaldehyde derivative (8, 1.0 mmol) and nitroolefin (3,1.5
mmol) were added in dry DCM (5 mL) in the presence of thiazolium
bromide 2c (9 mol %) and activated 4 Å MS (300 mg) under a
nitrogen atmosphere, and the mixture was stirred for 30 min. DABCO
(20 mol %) was added to the reaction mixture, and the mixture was
stirred at ambient temperature until the reaction was completed. The
reaction was monitored by TLC. The post reaction mixture was
filtered through a Celite bed, and the filtrate was extracted with
EtOAc (2 × 15 mL). The organic portion was washed with water (3
× 10 mL) and brine (1 × 10 mL). It was dried over Na2SO4, filtered,
and evaporated to dryness in a rotary evaporator under reduced
pressure at room temperature. The crude product was chromato-
graphed on silica gel (60−120 mesh) with ethyl acetate−petroleum
ether (10−30%, v/v) as an eluent, which afforded the corresponding
isoflavanones.
6-Chloro-3-(4-fluorophenyl)chroman-4-one (9f). Compound 9f
was prepared using 5-chlorosalicylaldehyde (8b) and 4-fluoro-β-
nitrostyrene (3b) as starting materials to give the product as a yellow
1
thick liquid: 67% yield (185 mg); H NMR (300 MHz, CDCl3) δ
4.38 (d, J = 12.1 Hz, 1H), 4.41−4.67 (m, 1H), 4.67−4.74 (m, 1H),
6.85−7.01 (m, 2H), 7.34−7.41 (m, 2H), 7.54−7.59 (m, 1H), 7.80−
7.81 (m, 1H), 7.91−7.93 (m, 1H); 13C NMR (75 MHz, CDCl3) δ
51.2, 73.7, 115.4, 115.9, 116.0, 119.7, 125.7, 126.8, 127.5, 127.7,
127.8, 127.9, 130.3, 130.5, 130.6, 133.9, 136.7, 152.9, 159.7, 164.5,
193.2; FTIR (neat, cm−1) 3082, 2908, 2868, 1688, 1582, 1483, 1355,
1267, 1065, 682, 575; HRMS (ESI) m/z calcd for C15H11ClFO2[M +
H]+ 277.0432, found 277.0435 (one of the major peaks).
6-Bromo-3-(4-fluorophenyl)chroman-4-one (9g). Compound 9g
was prepared using 5-bromosalicylaldehyde (8c) and 4-fluoro-β-
nitrostyrene (3b) as starting materials to give the product as a yellow
1
3-Phenylchroman-4-one (9a). Compound 9a was prepared using
salicyladehyde (8a) and β-nitrostyrene (3a) as starting materials to
give the product as a yellow solid: 72% yield (161 mg); mp 78−80 °C
thick liquid: 71% yield (226 mg); H NMR (300 MHz, CDCl3) δ
3.88−3.93 (m, 1H), 4.55−4.63 (m, 2H), 6.86 (d, J = 9.1 Hz, 1H),
6.95−7.01 (m, 2H), 7.15−7.19 (m, 2H), 7.51 (dd, J = 9.1 Hz, 3.6 Hz,
1H), 7.97 (d, J = 3.6 Hz, 1H); 13C NMR (75 MHz, CDCl3) δ 51.1,
71.3, 114.3, 115.7, 116.0, 119.9, 122.0, 130.0, 130.1, 138.7, 160.3,
160.7, 190.7; FTIR (neat, cm−1) 3026, 2870, 1688, 1622, 1580, 1472,
1326, 1286, 1210, 1146, 1035, 1012, 875, 762; HRMS (ESI) m/z
calcd for C15H11BrFO2 [M + H]+ 320.9926, found 320.9928 (one of
the major peaks).
6-Chloro-3-(2,6-difluorophenyl)chroman-4-one (9h). Compound
9h was prepared using 5-chlorosalicylaldehyde (8b) and 2,6-difluoro-
β-nitrostyrene (3g) as starting materials to give the product as a
yellow thick liquid: 75% yield (220 mg); 1H NMR (300 MHz,
CDCl3) δ 4.43−4.49 (m, 2H), 4.57 (d, J = 13.2 Hz, 1H), 6.74 (d, J =
8.7 Hz, 1H), 6.82−6.91 (m, 1H), 7.10−7.27 (m, 2H), 7.34−7.39 (m,
1H), 7.84 (d, J = 2.4 Hz, 1H); 13C NMR (75 MHz, CDCl3) δ 43.1,
69.4, 110.2, 111.5, 111.9, 118.2, 119.6, 120.8, 121.5, 126.8, 127.0,
127.1, 127.3, 129.9, 130.1, 130.2, 131.3, 135.9, 148.9, 159.8, 160.2,
163.0, 163.1, 188.8; FTIR (neat, cm−1) 3086, 2928, 2888, 1686, 1585,
1485, 1358, 1268, 1066, 683, 578; HRMS (ESI) m/z calcd for
C15H10ClF2O2 [M + H]+ 295.0337, found 295.0338 (one of the major
peaks).
(lit.33 77−78 °C); H NMR (300 MHz, CDCl3) δ 3.99−4.06 (m,
1
1H), 4.65−4.69 (m, 2H), 7.20−7.34 (m, 5H), 7.49−7.54 (m, 2H),
7.94−8.02 (m, 2H); 13C NMR (75 MHz, CDCl3) δ 51.9, 71.5, 119.8,
121.7, 123.0, 127.8, 128.4, 128.5, 128.9, 134.5, 135.8, 159.8, 191.3;
FTIR (KBr, cm−1) 3012, 2862, 1705, 1582, 1415, 1306, 1248, 1206;
HRMS (ESI) m/z calcd for C15H13O2[M + H]+ 225.0916, found
225.0915.
6-Chloro-3-phenylchroman-4-one (9b). Compound 9b was
prepared using 5-chlorosalicylaldehyde (8b) and β-nitrostyrene (3a)
as starting materials to give the product as a yellow solid: 82% yield
(211 mg); mp 100−102 °C (lit.33 99−101 °C); 1H NMR (300 MHz,
CDCl3) δ 3.87−3.92 (m, 1H), 4.56−4.60 (m, 2H), 6.87−6.91 (m,
1H), 7.15−7.18 (m, 3H), 7.22−7.27 (m, 2H), 7.27−7.38 (m, 1H),
7.82 (t, J = 5.7 Hz, 1H); 13C NMR (75 MHz, CDCl3) δ 51.9, 71.5,
119.5, 121.7, 126.9, 127.1, 126.9, 128.4, 128.4, 128.9, 134.4, 135.8,
159.9, 191.0; FTIR (KBr, cm−1) 3016, 2862, 1686, 1575, 1425, 1316,
1246, 1210, 786, 667; HRMS (ESI) m/z calcd for C15H12ClO2 [M +
H]+ 259.0526, found 259.0528 (one of the major peaks).
6-Bromo-3-phenylchroman-4-one (9c). Compound 9c was
prepared using 5-bromosalicylaldehyde (8c) and β-nitrostyrene (3a)
as starting materials to give the product as a yellow solid: 78% yield
(235 mg); mp 110−112 °C; 1H NMR (300 MHz, CDCl3) δ 3.99 (t, J
= 14.4 Hz, 1H), 4.67 (d, J = 7.5 Hz, 2H), 6.92 (d, J = 8.7 Hz, 1H),
7.25−7.29 (m, 3H), 7.31−7.39 (m, 3H), 7.57 (dd, J = 8.8 Hz, 2.7 Hz,
1H), 8.06 (d, J = 2.4 Hz, 1H); 13C NMR (75 MHz, CDCl3) δ 51.8,
71.4, 114.2, 119.9, 122.2, 127.9, 128.4, 128.9, 130.0, 134.4, 138.6,
160.4, 190.8; FTIR (KBr, cm−1) 3022, 2872, 1688, 1602, 1585, 1475,
8-Methyl-3-phenylchroman-4-one (9i). Compound 9i was pre-
pared using 2-hydroxy-3-methylbenzaldehyde (8f) as a starting
material to give the product as a thick liquid: 66% yield (156 mg);
1H NMR (300 MHz, CDCl3) δ 2.15 (s, 3H), 3.99 (t, J = 4.8 Hz, 1H),
4.66 (d, J = 15 Hz, 2H), 6.81 (t, J = 7.5 Hz, 1H), 7.27 (d, J = 7.5 Hz,
2H), 7.34−7.44 (m, 2H), 7.47−7.55 (m, 1H), 7.77 (d, J = 8.1 Hz,
2H); 13C NMR (75 MHz, CDCl3) δ 14.8, 50.0, 71.8, 119.8, 126.6,
128.3, 128.8, 129.6, 130.0, 131.2, 133.5, 134.3, 136.2, 137.7, 159.8,
H
J. Org. Chem. XXXX, XXX, XXX−XXX