European Journal of Organic Chemistry
10.1002/ejoc.201600975
FULL PAPER
3-Benzyl-2-phenyl-6,7-dihydrobenzofuran-4(5H)-one (IV g). The title
compound was obtained as a red solid (190mg, 63% yield). mp: 65 oC.
1H NMR (400 MHz, CDCl3) δ 7.47 – 7.38 (m, 4H), 7.38 – 7.29 (m, 3H),
7.29 – 7.19 (m, 3H), 4.00 (s, 2H), 2.89 (t, J = 6.3 Hz, 2H), 2.51 (t, J = 6.3
Hz, 2H), 2.27 – 2.10 (m, 2H); 13C NMR (101 MHz, CDCl3) δ 194.04,
166.48, 150.42, 138.00, 131.52, 129.82, 128.66, 128.45, 128.00, 127.41,
126.64, 120.52, 119.78, 38.66, 32.09, 23.78, 22.49; IR (KBr, cm-1): 3423,
3414, 1670, 1574, 1428, 1073, 1009, 773, 502; HRMS (ESI) calcd for
C21H19O2 (M+H)+: 303.1380, Found: 303.1378.
2-(2-Oxocyclohexyl)-1,3-diphenylpropane-1,3-dione (V g). The title
compound was obtained as white solid (118mg, 74% yield). mp: 54 oC.
1H NMR (400 MHz, CDCl3) δ 8.01(d, J = 7.4 Hz, 2H), 7.94 (d, J = 7.4 Hz,
2H), 7.57 (t, J = 7.4 Hz, 1H), 7.47 (q, J = 7.8 Hz, 3H), 7.37 (t, J = 7.7 Hz,
2H), 5.80 (d, J = 9.4 Hz, 1H), 3.85-3.68 (m, 1H), 2.59-2.37 (m, 2H), 2.21-
2.06 (m, 1H), 1.95-1.87 (m, 1H), 1.85-1.79 (m, 1H), 1.72-1.60 (m, 2H),
1.60-1.46 (m, 1H); 13C NMR (101 MHz, CDCl3) δ 210.60, 195.69, 194.28,
136.88, 136.69, 133.83, 133.16, 129.00, 128.80, 128.67, 128.56, 56.33,
52.65, 42.07, 31.96, 28.01, 25.34; IR (KBr, cm-1): 3434, 2938, 2869,
1712, 1697, 1447, 1282, 1195, 993, 707, 519;HRMS (ESI) calcd for
C21H21O3 (M+H)+: 321.1485, Found: 321.1488.
Ethyl 3-methyl-4-oxo-4,5,6,7-tetrahydrobenzofuran-2-carboxylate (IV
h)[27]. The title compound was obtained as colorless oil (166mg, 75%
yield). 1H NMR (400 MHz, CDCl3) δ 4.37 (q, J = 7.1 Hz, 2H), 2.91 (t, J =
6.3 Hz, 2H), 2.55 (s, 3H), 2.53 – 2.46 (m, 2H), 2.23 – 2.09 (m, 2H), 1.38
(t, J = 7.1 Hz, 3H); 13C NMR (101 MHz, CDCl3) δ 195.11, 168.69, 159.51,
140.19, 129.70, 121.72, 60.94, 38.41, 23.78, 22.20, 14.37, 10.39; MS
(ESI) calcd for C12H15O4 (M+H)+: 223.1, Found: 223.0.
2-(2-Oxocyclohexyl)-1-phenylbutane-1,3-dione (V h). The title
compound was obtained as a mixture of two diastereomers (82mg, 64%
yield, dr = 3 : 2). The sepctra data of the major isomer: 1H NMR (400
MHz, CDCl3) δ 8.10 – 7.85 (m, 2H), 7.68 – 7.41 (m, 3H), 5.01 (d, J = 10.0
Hz, 1H), 3.69 – 3.54 (m, 1H), 2.50 – 2.35 (m, 2H), 2.20 (s, 3H), 2.04 –
1.15 (m, 6H); 13C NMR (101 MHz, CDCl3) δ 211.25, 200.91, 195.30,
137.05, 134.04, 129.03, 128.78, 128.12, 61.80, 52.61, 42.07, 32.05,
28.13, 25.15; IR (KBr, cm-1): 2939, 1708, 1596, 1448, 1357, 1000, 753,
696; HRMS (ESI) calcd for C16H19O3 (M+H)+: 259.1329, Found: 259.1324.
Ethyl 4-oxo-4,5,6,7-tetrahydrobenzofuran-3-carboxylate (IV i)[28]. The
title compound was obtained as a yellow solid (158mg, 76% yield). mp:
58 oC. 1H NMR (400 MHz, CDCl3) δ 7.85 (s, 1H), 4.31 (q, J = 7.1 Hz, 2H),
2.88 (t, J = 6.3 Hz, 2H), 2.61 – 2.44 (m, 2H), 2.24 – 2.07 (m, 2H), 1.34 (t,
J = 7.1 Hz, 3H); 13C NMR (101 MHz, CDCl3) δ 191.98, 168.33, 161.91,
147.77, 118.73, 117.48, 60.94, 38.71, 23.60, 22.17, 14.19; IR (KBr, cm-
1):3451, 3120, 1736, 1554, 1455, 1300, 1183, 1002, 878, 769, 586;
HRMS (ESI) calcd for C11H13O4 (M+H)+: 209.0808, Found: 209.0803.
Diethyl 2-(2-oxocyclohexyl)malonate (V i)[30]. The title compound was
obtained as yellowish oil (89mg, 70% yield). 1H NMR (400 MHz, CDCl3) δ
4.30 – 4.06 (m, 4H), 3.63 (d, J = 9.6 Hz, 1H), 3.18 (ddd, J = 13.2, 9.6, 5.5
Hz, 1H), 2.50 – 2.34 (m, 2H), 2.19 – 2.08 (m, 1H), 2.03 (ddd, J = 12.5,
5.4, 2.6 Hz, 1H), 1.95-1.85 m, 1H), 1.72 – 1.62 (m, 3H), 1.25 (ddd, J =
8.2, 7.1, 4.1 Hz, 6H); 13C NMR (101 MHz, CDCl3) δ 209.80, 168.59,
168.39, 61.53, 52.30, 50.31, 41.93, 31.18, 27.81, 25.07, 14.12, 14.02; IR
(KBr, cm-1): 2940,2864, 1801, ,1732, 1448, 1368, 1231, 1038, 861, 526;
MS (ESI) calcd for C13H21O5 (M+H)+: 257.1, Found: 257.1.
2,3,4,6,7,8,9,10-Octahydro-1H-cyclohepta[b] benzofuran-1-one (IV j).
The reaction procedure was the same as that of IVb. To the solution of
dihydrofuran III g (0.5 mmol) in dichloromethane (2 mL) was added one-
drop of concentrated hydrochloric acid. Finally, the title compound was
obtained as yellowish oil (165mg, 81% yield). 1H NMR (400 MHz, CDCl3)
δ 2.87 – 2.80 (m, 2H), 2.77 (t, J = 6.3 Hz, 2H), 2.75 – 2.69 (m, 2H), 2.46
– 2.37 (m, 2H), 2.15 – 2.04 (m, 2H), 1.80 – 1.70 (m, 2H), 1.70 – 1.60 (m,
4H); 13C NMR (101 MHz, CDCl3) δ 196.15, 164.26, 153.49, 120.74,
119.18, 38.52, 30.55, 28.53, 28.34, 26.33, 23.52, 23.51, 22.77; IR (KBr,
cm-1): 2918, 2844, 1667, 1577, 1369, 1046, 833, 645; HRMS (ESI) calcd
for C13H17O2 (M+H)+: 205.1223, Found: 205.1220.
Ethyl 3-oxo-2-(2-oxocyclopentyl)butanoate (V j). Two diastereomers
were obtained (70% yield, dr = 1 : 3). The upper spot (24mg, 23% yield):
1H NMR (400 MHz, CDCl3) δ 4.23 (q, J = 7.1 Hz, 2H), 4.16 (q, J = 7.1 Hz,
2H), 3.87 – 3.78 (m, 2H), 2.86 – 2.75 (m, 1H), 2.67 (d, J = 5.9 Hz, 1H),
2.31 (s, 3H), 2.38-2.27 (m, 2H), 2.22 (s, 3H), 2.27-2.17 (m, 2H), 2.15-
2.03 (m, 2H), 1.87-1.75 (m, 2H), 1.75-1.65 (m, 2H), 1.28 (t, J = 7.1 Hz,
3H), 1.24 (t, J = 7.1 Hz, 3H); 13C NMR (101 MHz, CDCl3) δ 217.81,
202.16, 201.61, 169.16, 168.22, 61.65, 61.58, 58.97, 58.41, 48.62, 48.54,
37.29, 37.03, 30.25, 29.51, 26.77, 26.51, 20.72, 20.68, 14.04; HRMS
(ESI) calcd for C11H17O4 (M+H)+: 213.1121, Found: 213.1129.
Greneral procedure for the one-pot synthesis of furan (Table 4).
A 4 mL vial equipped with a magnetic stir bar was charged with base (0.6
mmol), dicarbonyl compound II (0.5 mmol) and solvent (2 mL). Fresh
distilled α-haloketone I (0.5 mmol) was added to the reaction mixture and
stirred at 40-60 oC under argon. After completion of the reaction
(monitored by TLC), the reaction mixture was concentrated under
reduced pressure. The concentrated mixture was added water and
extracted by dichloromethane. The organic layer was washed with brine,
dried over anhydrous sodium sulfate and evaporated under reduced
pressure. The concentrated residue was seperated by silica-gel column
chromatography using ethyl acetate−hexane as eluent in increasing
polarity to yield the desired tricarbonyl compound.
The lower spot (59mg, 56% yield): 1H NMR (400 MHz, CDCl3) δ 4.23 (q,
J = 7.1 Hz, 2H), 4.18 (q, J = 7.1 Hz, 2H), 3.42 (d, J = 6.3 Hz, 1H), 3.40 (d,
J = 6.4 Hz, 1H), 2.93 – 2.78 (m, 2H), 2.48 (d, J = 7.5 Hz, 1H), 2.43 (d, J =
7.5 Hz, 1H), 2.37-2.11 (m, 6H), 2.24 (s, 3H), 2.22 (s, 3H), 1.94 (ddd, J =
18.4, 11.1, 1.2 Hz, 1H), 1.80 (ddd, J = 18.3, 11.0, 1.2 Hz, 1H), 1.66 –
1.45 (m, 2H), 1.28(t, J = 7.1 Hz, 3H), 1.26(t, J = 7.1 Hz, 3H); 13C NMR
(101 MHz, CDCl3) δ 217.11, 217.07, 201.61, 201.45, 168.41, 168.33,
64.83, 64.61, 61.73, 61.71, 42.96, 42.71, 38.17, 38.02, 35.85, 35.76,
29.47, 29.23, 27.62, 27.34, 14.12, 14.08; HRMS (ESI) calcd for C11H17O4
(M+H)+: 213.1121, Found: 213.1126.
3-(2-Oxocyclohexyl)pentane-2,4-dione (V f)[29]. The title compound
was obtained as yellowish solid (77mg, 79% yield). mp: 50 oC. 1H NMR
(400 MHz, CDCl3) δ 3.96 (d, J = 10.2 Hz, 1H), 3.36 (ddd, J = 13.2, 10.7,
5.3 Hz, 1H), 2.42 – 2.34 (m, 2H), 2.28 (s, 3H), 2.17 (d, J = 4.5 Hz, 3H),
2.14-2.05 (m, 1H), 1.96-1.82 (m, 2H), 1.77-1.51 (m, 2H), 1.33 (dd, J =
12.8, 3.5 Hz, 1H); 13C NMR (101 MHz, CDCl3) δ 210.22, 202.95, 202.50,
69.36, 51.96, 41.90, 31.62, 30.48, 29.27, 27.75, 25.05; IR (KBr, cm-
1):2947, 2862, 1693, 1427, 1356, 1208, 1157, 517; MS (ESI) calcd for
C11H17O3 (M+H)+: 197.1, Found: 197.1.
3-(2-Oxocyclopentyl)pentane-2,4-dione (V k)[29]. The title compound
was obtained as yellowish oil (73mg, 80% yield). 1H NMR (400 MHz,
CDCl3) δ 4.49-4.40 (m, 1H), 3.92 (d, J = 7.5 Hz, 1H), 2.44 – 2.34 (m, 2H),
2.27 (s, 3H), 2.21 (dt, J = 9.3, 3.8 Hz, 3H), 2.14 (s, 3H), 2.10-2.02 (m,
2H); 13C NMR (101 MHz, CDCl3) δ 217.89, 203.53, 202.64, 67.72, 49.02,
36.95, 30.09, 29.51, 26.75, 20.71; IR (KBr, cm-1): 3466, 2964, 1697,
1359, 1161, 981, 584, 490; HRMS (ESI) calcd for C10H15O3 (M+H)+:
183.1016, Found: 183.1013.
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