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General Experimental
Procedure
The reaction was carried out in a HF-15
autoclave. Pd(OAc)2 (4.49 mg, 0.02 mmol), Zn(OTf)2 (98.3
mg, 0.3 mmol), MeOH (3 mL), and alkyne (1 mmol) were added into
a 15 mL autoclave in sequence. Oxygen was pumped into the autoclave
by a cooling pump to reach the desired pressure, then the autoclave
was heated by oil bath under magnetic stirring for the desired reaction
time. After the reaction finished, the autoclave was allowed to
cool to 0 ˚C. Residual O2 was vented,
and the surplus was filtrated and condensed under reduced pressure.
The product was purified by chromatography on a SiO2 column
using light PE-CH2Cl2
as
eluent.
<A NAME="RW18308ST-8">8</A>
Spectroscopic Data
for Tetrasubstituted Furans
2,3,4,5-Tetrakis(4-methoxyphenyl)furan
¹³
Mp 206-208 ˚C. ¹H
NMR (400 MHz, CDCl3): δ = 3.78 (s, 12
H), 6.77 (d, J = 6.4
Hz, 4 H), 6.79 (d, J = 7.2
Hz, 4 H), 7.04 (d, J = 8.8
Hz, 4 H), 7.42 (d, J = 9.2
Hz, 4 H) ppm.
¹³C NMR (100
MHz, CDCl3): δ = 125.1, 125.8, 127.1,
127.3, 128.3, 128.5, 130.4, 130.9, 133.1, 147.7 ppm. MS (EI, 70 eV): m/z (%) = 492
(28) [M+], 318 (100), 275
(31), 135 (47).
2,3,4,5-Tetrakis(4-fluorophenyl)furan
¹4
¹H NMR (400
MHz, CDCl3): δ = 6.93 (m, 8 H), 7.05-7.08 (m,
4 H), 7.41-7.44 (m, 4 H) ppm. ¹³C
NMR (100 MHz, CDCl3): δ = 115.6 (t, J = 80 Hz),
123.5, 126.7, 127.6, 127.7, 128.6, 131.9, 147.1, 160.9, 163.4 ppm.
MS (EI, 70 eV):
m/z (%) = 444
(100) [M+], 321 (73), 123
(69), 95 (55).
2,3,4,5-Tetrakis[4-(trifluoromethyl)phenyl]furan
¹³
Mp
195-197 ˚C. ¹H NMR (400 MHz,
CDCl3): δ = 7.24 6 (d, J = 8.0 Hz,
4 H), 7.55-7.57 (m, 12 H) ppm. ¹³C
NMR (100 MHz, CDCl3): δ = 119.9, 122.6,
125.1, 125.3, 125.7, 125.9, 126.2, 127.3, 128.0, 129.0, 129.8, 129.9,
130.1, 130.5, 130.8, 133.0, 135.6, 148.0 ppm. MS (EI, 70 eV): m/z (%) = 644
(46) [M+], 471 (13), 173 (100),
145 (33).
2,3,4,5-Tetra-
m
-tolylfuran
¹5
Mp 100-102 ˚C. ¹H
NMR (400 MHz, CDCl3): δ = 2.17 (s,
6 H), 2.27 (s, 6 H), 6.91-7.22 (m, 12 H), 7.62-7.66
(m, 4 H) ppm. ¹³C NMR (100 MHz, CDCl3): δ = 21.3,
29.7, 123.0, 127.0, 127.6, 127.9, 128.1, 129.0, 129.2, 130.1, 130.2,
133.7, 135.3, 136.4, 137.9, 138.14, 144.2 ppm. MS (EI, 70 eV):
m/z (%) = 428
(100) [M+], 309 (21), 119
(65), 91 (18).
<A NAME="RW18308ST-9">9</A>
Procedure for Cyclization
of 1,4-Dione A
The reaction was carried out in a HF-15
autoclave. Pd(OAc)2 (4.49 mg, 0.02 mmol), Zn(OTf)2 (98.3
mg, 0.3 mmol), MeOH (3 mL), and 1,4-dione A (388
mg, 1 mmol) were added into a 15 mL autoclave in sequence. Oxygen
was pumped into the autoclave by a cooling pump to reach the desired
pressure, then the autoclave was heated by oil bath under magnetic
stirring for the desired reaction time. After the reaction finished,
the autoclave was allowed to cool to
0 ˚C. Oxygen
was vented, and the surplus was filtrated and condensed under reduced
pressure. The product was purified by chromatography on a SiO2 column
using light PE-CH2Cl2 as eluent to
give 2a in 72% yield.
<A NAME="RW18308ST-10">10</A>
Spectroscopic
Data for (
Z
)-1,2,3,4-Tetraphenylbut-2-ene-1,4-dione
¹6
Mp
216-217 ˚C. ¹H NMR (400 MHz,
CDCl3): δ = 7.14-7.40 (m,
16 H), 7.82-7.84 (m, 4 H) ppm. ¹³C
NMR (100 MHz, CDCl3): δ = 128.3, 128.4,
128.5, 128.6, 129.8, 130.0, 133.0, 135.2, 136.3, 144.6, 196.9 ppm.
MS (EI, 70 eV): m/z (%) = 388
(12) [M+], 178 (9), 105 (100),
77 (43).
The formation of 1,4-dione from
tetraphenylcyclobuta-dienenickel and palladium complex, see:
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Aradi AA.
Boleslawski MP.
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1980,
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105
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of 1,4-dicarbonyl compounds to synthesize furans, see:
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