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Khusnutdinov et al.
as the stationary phase, temperature rise from 50 to 270 C,
heating rate 8 deg min–1, helium as a carrier gas (47 mL min–1)).
Elemental analysis was carried out on a Carlo Erba analyzer
(model 1106).
Commercially available starting materials (furan (1),
2ꢀacetylfuran (5), furfural (7), 2ꢀmethylfuran (11), methanol,
and carbon tetrachloride) were distilled or recrystallized beꢀ
fore use.
Furanꢀ2ꢀcarboxylic acid (4) was prepared by oxidation of
furfural (7) according to a known procedure.21 Methyl furanꢀ2ꢀ
carboxylate (3) was synthesized by esterification of acid 4.22
Copperꢀcontaining catalysts (CuI, CuBr2, Cu(acac)2, and
Cu(OAc)2) were used as purchased.
C, 52.75; H, 5.89; O, 41.36. C9H12O5 (M = 200.19). Calculatꢀ
ed (%): C, 54.00; H, 6.04; O, 39.96.
Methyl 5ꢀformylfuranꢀ2ꢀcarboxylate (9) (see Ref. 26) was
synthesized under the following conditions: [CuI] : [furfural] :
: [CCl4] : [MeOH] = 1 : 100 : 750 : 500, 160 C, 6 h. Yield 33%,
m.p. 91.5 C. 1H NMR (CDCl3), : 3.95 (s, 3 H, CO2Me); 7.27
(s, 2 H, furan); 9.80 (s, 1 H, CHO). 13C NMR (CDCl3), : 52.57
(CO2CH3), 118.67 (C(3)), 118.94 (C(4)), 147.61 (C(2)), 153.84
(C(5)), 158.39 (CO2Me), 178.95 (CHO). MS (EI, 70 eV), m/z
(Irel (%)): 154.15 [M]+ (65.43), 123.15 (100.00), 153.10 (11.43),
124.15 (17.59), 67.05 (7.25), 53.05 (4.56), 39.05 (20.24),
37.05 (4.37).
Furfural dimethyl acetal (10) was synthesized under the folꢀ
Carboxylation of furan and its derivatives (general procedure).
Reactions were carried out in 10ꢀmL glass tubes inside a 17ꢀmL
stainless steel microautoclave with continuous stirring and conꢀ
trolled heating.
lowing conditions: [CuI] : [furfural] : [CCl4] : [MeOH] =
= 1 : 100 : 750 : 6500, 100 C, 6 h. Yield 62%, b.p. 80 C
(50 Torr).27 1H NMR (CDCl3), : 3.34 (s, 6 H, CH(OCH3)2);
5.42 (s, 1 H, CH(OMe)2); 6.34—6.44 (m, 2 H, furan); 7.39 (d, 1 H,
C(5)H, J = 3.3 Hz). 13C NMR (CDCl3), : 53.49 (CH(OCH3)2),
97.51 (CH(OMe)2), 109.18 (C(3)), 109.93 (C(4)), 143.20 (C(5)),
150.35 (C(2)).
Methyl 5ꢀmethylfuranꢀ2ꢀcarboxylate (12) was synthesized
under the following conditions: [CuI] : [2ꢀmethylfuran] : [CCl4] :
: [MeOH] = 1 : 100 : 750 : 1125, 90 C, 6 h. Yield 38%, b.p.
78—84 C (11 Torr).28 1H NMR (CDCl3), : 2.36 (s, 3 H, Me);
3.85 (s, 3 H, CO2Me); 6.1 (d, 1 H, furan, J = 3.6 Hz), 7.06
(d, 1 H, furan, J = 3.6 Hz). 13C NMR (CDCl3), : 14.15 (Me),
51.68 (CO2CH3), 108.42 (C(4)), 119.44 (C(3)), 142.93 (C(5)),
157.15 (C(2)), 159.18 (CO2Me). MS (EI, 70 eV), m/z (Irel (%)):
140 [M]+ (42), 109 (100), 82 (8), 53 (13), 43 (4).
A tube was charged under argon with a copperꢀcontainꢀ
ing catalyst (0.01 mmol), CCl4 (2—7.5 mmol), methanol
(8—65 mmol), and furan (or its derivative) (1 mmol). The tube
was sealed and placed in the autoclave. The autoclave was
hermetically closed and the reaction mixture was stirred at
90—150 C for 6—9 h. After completion of the reaction, the
autoclave was cooled to 20 C and the tube was opened. The
reaction mixture was passed through a short column of Al2O3
and neutralized with aqueous Na2CO3. The product was exꢀ
tracted with CHCl3 and recrystallized from diethyl ether (for
solids) or distilled in vacuo (for liquids).
The structures of the compounds obtained were proved by
NMR spectroscopy and mass spectrometry.
Dimethyl furanꢀ2,5ꢀdicarboxylate (2) was synthesized under
the following conditions: [Cu(acac)2] : [furanꢀ2ꢀcarboxylic
acid] : [CCl4] : [MeOH] = 1 : 100 : 750 : 1125, 150 C, 6 h. Yield
95%, m.p. 110—112 C (cf. Refs 23 and 24: m.p. 112 and
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 12ꢀ03ꢀ00183ꢀa).
References
1
110—111 C, respectively). H NMR (CDCl3), : 3.91 (s, 6 H,
Me); 7.2 (s, 2 H, CH, furan). 13C NMR (CDCl3), : 52.35
(CO2CH3), 118.49 (C(3), C(4)), 146.64 (C(2), C(5)), 158.38
(CO2Me). MS (EI, 70 eV), m/z (Irel (%)): 184 [M]+ (33), 154
(15), 153 (100), 126 (11), 95 (11), 75 (4), 59 (8), 43 (2).
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Methyl 5ꢀacetylfuranꢀ2ꢀcarboxylate (6) was synthesized unꢀ
der the following conditions: [Cu(acac)2] : [2ꢀacetylfuran] :
: [CCl4] : [MeOH] = 1 : 100 : 200 : 800, 120 C, 9 h. Yield 90%,
m.p. 100.5—101 C (cf. Ref. 25: m.p. 101—102 C). 1H NMR
(CDCl3), : 2.55 (s, 3 H, MeCO); 3.92 (s, 3 H, OMe); 7.20 (d, 1 H,
CH, furan, J = 3.2 Hz); 7.23 (d, 1 H, CH, furan, J = 3.2 Hz).
13C NMR (CDCl3), : 25.85 (COCH3), 52.17 (CO2CH3), 115.43
(C(4)), 118.38 (C(3)), 145.90 (C(2)), 154.55 (C(5)), 158.42
(CO2Me), 187.12 (COMe). MS (EI, 70 eV), m/z (Irel (%)): 168
[M]+ (42), 153 (100), 137 (20), 125 (4), 95 (21), 79 (5), 69 (12),
59 (10), 43 (30).
Methyl 5ꢀdimethoxymethylfuranꢀ2ꢀcarboxylate (8) was synꢀ
thesized under the following conditions: [Cu(acac)2] : [furfural] :
: [CCl4] : [MeOH] = 1 : 100 : 750 : 6500, 150 C, 6 h. Yield 86%.
1H NMR (CDCl3), : 3.37 (s, 6 H, CH(OCH3)2); 3.89 (s, 3 H,
CO2Me); 5.45 (s, 1 H, CH(OMe)2); 6.54 (d, 1 H, furan,
J = 3.2 Hz), 7.16 (d, 1 H, furan, J = 3.6 Hz). 13C NMR (CDCl3),
: 51.91 (CO2CH3), 53.07 (CH(OCH3)2), 97.54 (CH(OMe)2),
110.38 (C(4)), 118.38 (C(3)), 144.30 (C(2)), 155.05 (C(5)),
159.00 (CO2Me). MS (EI, 70 eV), m/z (Irel (%)): 200.10 [M]+
(9.46), 168.90 (100.00), 152.95 (2.84), 141.00 (9.76), 123.00
(15.77), 110.00 (2.46), 94.95 (4.16), 75.00 (8.23). Found (%):