Li, Yuan & Jiang
FULL PAPER
oxylic acid (3c) 1H NMR (DMSO-d6, 400 MHz) δ:
12.4 (s, 1H), 7.28—7.46 (m, 10H), 4.35 (s, 1H); 13C
NMR (DMSO-d6, 100 MHz) δ: 174.1, 172.4, 169.2,
136.0, 135.7, 128.9, 128.7, 128.3, 128.0, 127.7, 127.0,
metal salt was completely dissolved in DMF. After the
cell was assembled, CO2 was charged into the cell at the
desired pressure. The reaction was carried out at-suit-
1
able constant current. When the charge (4 F•mol of
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65.+2, 54.3; IR (KBr) v: 1760, 1689 cm ; MS m/z: 296
substrate) passed through the cell, the reaction was
stopped. After the electrolyte was distilled at reduced
pressure, the residue was acidified with hydrochloric
(M ).
Dihydro-3-(4-nitrophenyl)furan-2.5-dione
(2d)
1H NMR (DMSO-d6, 400 MHz) δ: 7.25—7.35 (m, 4H),
3.86 (dd, J=5.2, 11.2 Hz, 1H), 2.95 (dd, J=9.6, 16.4
Hz, 1H), 2.53 (dd, J=5.6, 17.2 Hz, 1H); 13C NMR
(DMSO-d6, 100 MHz) δ: 173.3, 169.3, 136.8, 135.5,
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acid (1.0 mol•L ) and continuously stirred for 3 h. The
acidic solution was extracted with diethyl ether (25 mL
×4). The ether phase was washed two times with dis-
tilled water and dried over anhydrous MgSO4. After
evaporation of ether, the obtained crude products were
separated by re-crystallization or thin layer chromatog-
raphy and column chromatography, with the suitable
ratio of petroleum ether-ethyl acetate as eluent, and then
dried at 60 ℃ in a vacuum oven.
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128.1, 127.8, 46+.7, 37.2; IR (KBr) v: 1753, 1685 cm ;
MS m/z: 221 (M ).
Tetrahydro-4-(4-nitrophenyl)-2,5-dioxofuran-3-
carboxylic acid (3d) 1H NMR (DMSO-d6, 400 MHz)
δ: 12.3 (s, 1H), 8.11—8.39 (m, 4H), 3.95 (d, J=4 Hz,
1H), 3.53 (d, J=4.4 Hz, 1H); 13C NMR (DMSO-d6, 100
MHz) δ: 173.2, 165.9, 163.6, 139.5, 136.9, 129.0, 122.6,
Characterizations of products
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Mass spectra analyses were done on a Shimadzu
QP5050A spectrometer. FTIR spectra were measured
47.+6, 42.8; IR (KBr) v: 1766, 1700 cm ; MS m/z: 265
(M ).
1
by a TENSOR27 spectrometer. H NMR and 13C NMR
were determined on a Bruker DRX-400 spectrometer
with DMSO-d6 as the solvent in the presence of SiMe4
as an internal standard. Spectroscopic data of the pre-
pared compounds were given as follows.
Results and discussion
Effect of metal salt catalysts
The experimental results have shown that the forma-
tion of the tricarboxylic acid 3a depended on the influ-
ence of metal salts to some extent. Hence, we selected
phenylacetylene (model molecule) to investigate the
influence of metal salts. As shown in Table 1. Among
these metal salts (CuI, FeCl3, CuCl2, FeCl2 and
Pd(OAc)2), CuI exhibited good catalytic activation, the
yield of 3a could reach 70% (Table 1, Entry 1). With
FeCl3, CuCl2 and FeCl2, the yields of 3a were 61%, 52%
and 50%, respectively (Table 1, Entries 2—4). In con-
trast, with Pd(OAc)2 as catalyst, low yield 3a was ob-
tained in 31% (Table 1, Entry 5) because there was
black substances clung+to the surface of the cathode due
to the reduction of Pd2 so that the voltage between the
anode and cathode increased dramatically leading to the
Dihydro-3-phenylfuran-2,5-dione (2a) 1H NMR
(DMSO-d6, 400 MHz) δ: 7.25—7.35 (m, 5H), 3.90 (dd,
J=5.6, 11.6 Hz, 1H), 2.95 (dd, J=10, 16.8 Hz, 1H),
2.53 (dd, J=5.2, 16.8 Hz, 1H); 13C NMR (DMSO-d6,
100 MHz) δ: 173.0, 169.0, 135.9, 128.3, 127.7, 127.0,
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46.+8, 37.4; IR (KBr) v: 1763, 1695 cm ; MS m/z: 176
(M ).
Tetrahydro-2,5-dioxo-4-phenylfuran-3-carboxyl-
ic acid (3a) 1H NMR (DMSO-d6, 400 MHz) δ: 12.3 (s,
1H), 7.26—7.33 (m, 5H), 4.01 (d, J=7.6 Hz, 1H), 3.90
(d, J=5.6 Hz, 1H); 13C NMR (DMSO-d6, 100 MHz) δ:
174.0, 172.6, 168.4, 138.7, 128.6, 127.7, 127.2, 5+5.3,
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50.5; IR (KBr) v: 1765, 1700 cm ; MS m/z: 220 (M ).
Dihydro-3-p-tolylphenylfuran-2,5-dione (2b) 1H
NMR (DMSO-d6, 400 MHz) δ: 7.10—7.15 (m, 4H),
3.83 (dd, J=2.4, 7.6 Hz, 1H), 2.1 (dd, J=10.0, 16.8 Hz,
1H), 2.51 (dd, J = 5.6, 11.2 Hz, 1H); 13C NMR
(DMSO-d6, 100 MHz) δ: 173.1, 169.2, 136.3, 132.8,
129.1, 127.6, 46.4, 37.+4, 20.6; IR (KBr) v: 1772, 1680
Table 1 Effect of various metal salt catalysts on the electrocar-
boxylation of phenylacetylene with CO2
a
Entry Catalystb
Yield of 2ac/%
Yield of 3ac/% η /%
d
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1
2
3
4
5
CuI
FeCl3
27
30
26
27
5
70
61
52
50
31
73
68
59
58
27
cm ; MS m/z: 190 (M ).
Tetrahydro-2,5-dioxo-4-p-tolylfuran-3-carboxyl-
ic acid (3b) 1H NMR (DMSO-d6, 400 MHz) δ: 12.6 (s,
1H), 7.12—7.16 (m, 4H), 3.94 (d, J=11.6 Hz, 1H),
3.85 (d, J=9.6 Hz, 1H); 13C NMR (DMSO-d6, 100
MHz) δ: 174.1, 172.6, 168.4, 136.9, 135.6, 1-29.1, 128.2,
CuCl2
FeCl2
Pd(OAc)2
a Experimental conditions: phenylacetylene (2 mmol), DMF (35
mL), CO2 4 MPa, room temperature, n-Bu4NBr (2.5 mmol), elec-
tricity (4 F•mol- 1), current density 10 mA•cm- 2, Ni cathode and
Al anode; b Metal salt catalyst (0.1 equiv.); c Total isolated yield
based on phenylacetylene and the yield of 2a and 3a were deter-
1
55.3, 50.1, 20.6; IR (KBr) v: 1768, 1702 cm ; MS m/z:
234 (M+).
Dihydro-3,4-diphenylfuran-2,5-dione (2c)
1H
NMR (DMSO-d6, 400 MHz) δ: 7.28—7.46 (m, 10H),
4.23 (s, 2H); 13C NMR (DMSO-d6, 100 MHz) δ: 172.4,
137.3, 128.6, 128.0, 12+7.0, 53.4; IR (KBr) v: 1763, 1675
d
mined by GC-MS; η=Q1/Q2 (η: Current efficiency; Q1: Quan-
tity of electricity consumed in forming product; Q2: Total elec-
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cm ; MS m/z: 252 (M ).
tricity quantity in the electrolysis).
Tetrahydro-2,5-dioxo-3,4-diphenylfuran-3-carb-
1686
© 2010 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2010, 28, 1685— 1689