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J. Chem. Sci. (2018) 130:67
with a Shimadzu IR Prestige-21 FTIR spectrometer. UV-Vis 2.4 Synthesis of 4,4ꢀ-dinitro-2,2ꢀ- bipyridine-N,Nꢀ
-dioxide (5) and 4,4ꢀ-dinitro-2,2ꢀ-bipyridine (5a)
Data were obtained with a WTW photolab 6600 UV-Vis spec-
trometer. NMR data were recorded on a Bruker DRX 400
spectrometer (1H: 400.13 MHz; 13C: 100.62 MHz; CDCl3 as 5 and 5a were synthesized according to a modified litera-
internal standard).
ture procedure.18,19 1.0 g (5.3 mmol) 4 was dissolved in a
mixture of 0.4 cm3 oleum and 4.2 cm3concentrated sulfu-
◦
ric acid and cooled to 0 C in an ice bath. 2.2 cm3 fuming
2.2 Synthesis of diethyl
nitric acid were added carefully. The reaction mixture was
2-(2,2ꢀ-bipyridin-4-ylmethylene)malonate (3)
◦
heated to 100 C overnight. Subsequently the reaction mix-
ture was cooled to 0 ◦C using an ice bath before it was poured
on 20 g crushed ice. Liquid nitrogen was added immediately
to freeze the reaction mixture. After warming to room tem-
perature, liquid nitrogen was added again. While warming to
room temperature a slightly yellow precipitate formed, which
was collected and washed with water. The crude product
persisted of a mixture of 5 and 5a and was used for fur-
ther reactions without purification. Yield: 40% (0.6 g, 2.16
mmol).
0.5 cm3 (2.5 mmol) diethyl malonate, one drop of piperidine,
one drop of acetic acid and 0.46 g (2.5 mmol) 2,2ꢀ-bipyridine-
4-carbaldehyde17 were dissolved in 10 cm3 n-heptane. The
reaction mixture was heated to reflux for 17 h. After cool-
ing to room temperature 10 cm3 distilled water and 10 cm3
methyl tert-butyl ether were added. The organic layer was
separated and washed with 10 cm3 water and 10 cm3 brine.
The organic layer was dried over sodium sulfate and the
solvent was evaporated. The crude product was purified by
column chromatography using alumina as stationary phase
and a mixture of diethyl ether and toluene (1:2) as eluent. The
product was recrystallized from an ethanol water mixture by
dissolving the product first in ethanol and adding water until
the solution turned cloudy. Yield: 14% (0.12 g, 0.35 mmol).
IR (298 K) [cm−1]: 2995w, 2970w, 2936w, 1715vs, 1697s,
1643m, 1589m, 1547m, 1450m, 1364s, 1317s, 1206s, 1177vs,
1028m, 982m, 839s; MS (EI), m/z (%): 327 (1) [MH+], 297
(65) [M+- C2H5], 282 (62) [MH+- C2H5O], 269 (65) [M+-
2 C2H5], 253 (80) [MH+- C2H5O - C2H5], 235 (30) [MH+-
2 C2H5OH], 225 (100) [MH+- C3H5O2 - C2H5], 210 (100)
[C13H10N2O+], 182 (95) [C10H9N+2 ], 156 (15) [C10H8N2+];
1H-NMR (CDCl3): δ [ppm] = 1.32 (t, J= 7.07 Hz, 3 H), 1.36
(t, J= 7.20 Hz, 3 H), 4.34 (q, J= 1.00 Hz, 2 H), 4.39 (q, J=
1.00 Hz, 2 H), 7.31–7.36 (m, 2 H), 7.76 (s, 1 H), 7.83 (td, J=
7.77, 1.89 Hz, 1 H), 8.40 (dt, J= 7.89, 0.98 Hz, 1 H), 8.48
–8.51 (m, 1 H), 8.66–8.69 (m, 1 H), 8.71 (d, J= 5.31 Hz, 1
H); 13C-NMR (CDCl3): δ [ppm] = 13.8, 14.1, 62.0, 120.6,
121.0, 122.4, 124.0, 130.5, 136.9, 139.3, 141.3, 149.2, 149.7,
155.3, 157.0, 163.4, 165.6; M.p.: 65–67 ◦C; elemental anal-
ysis: calc. (%) for C18H18N2O4: C 66.25, H 5.56, N 8.58;
found: C 67.94, H 5.65, N 8.85.
2.5 Synthesis of 4,4ꢀ-dibromo-2,2ꢀ-bipyridine (6)
6 was synthesized according to a modified literature proce-
dure.20 0.9 g (3.2 mmol) of a mixture consisting of 5 and 5a
were suspended in 20 cm3 glacial acetic acid in a microwave
vessel and 3 cm3 (40.5 mmol) acetyl bromide were added. The
mixture turned yellow immediately and the microwave vessel
was sealed before it was heated to 130 ◦C within ten minutes
and a maximum power of 1000 MW. The reaction tempera-
ture then was maintained for 2 h after which the vessel was
allowed to cool to room temperature. The reaction mixture
was basified with a concentrated K2CO3 solution so that a
brownish precipitate formed. The precipitate was collected,
washed with water and dried. For purification, the crude prod-
uct was dissolved in dichloromethane and filtered. After the
solvent was evaporated product was further purified by distil-
lation under reduced pressure to obtain as white solid. Single
crystals of (6) were obtained by dissolving a sample of the
compound in the minimum amount of ethanol, adding water
until a low haze was observed and storing the solution in a
refrigerator (4 ◦C) overnight. Yield: 81% (0.825 g, 2.6 mmol);
melting point: 141–142 ◦C, literature: 135–136 ◦C.21
2.6 Synthesis of 2,2ꢀ-bipyridine-4,4ꢀ-dicarbaldehyde
(7)
2.3 Synthesis of 2,2ꢀ-bipyridine-N,Nꢀ-dioxide (4)
4 was synthesized according to a modified literature proce-
dure.18 2 g (12.8 mmol) 2,2ꢀ-bipyridine were suspended in 7 was synthesized before by applying other methodolo-
15 cm3 concentrated acetic acid in a microwave vessel and gies.22,23 0.9 g of 6 (2.9 mmol) were dissolved in 25 cm3
5 cm3 (49 mmol) of 30% H2O2 were added dropwise. The anhydrous diethyl ether and 25 cm3 anhydrous toluene under
microwave vessel was sealed and heated to 100 ◦C within 20 a nitrogen atmosphere at -78 ◦C. Butyl lithium in hexane (5
min using a maximum power of 1000 MW. The temperature cm3, 2.5 mol/L) was added dropwise. The solution was stirred
was held for one hour and forty minutes. After cooling to at -78 ◦C for 90 min before 8.0 cm3 anhydrous dimethyl for-
room temperature, the mixture was mixed with 170 cm3 ace- mamide were added. The resulting solution was then stirred
tone leading to the immediate formation of a white precipitate. for another 90 min at the same temperature. To stop the reac-
The mixture was cooled for an additional hour in an ice bath tion 50 cm3 2 N hydrochloric acid were added at -78 ◦C and
before the precipitate was collected, washed with acetone and the solution was then allowed to reach room temperature. The
air dried. Yield: 97% (2.39 g, 12.7 mmol); melting point: 303 organic phase was separated and the aqueous phase was neu-
◦C (decomp.), literature: 307–309 ◦C.19
tralized with diluted sodium hydroxide solution. A smooth