MOLECULAR COMPLEXES OF 4-NITROPYRIDINE AND 4-NITROQUINOLINE N-OXIDES
1829
a Specord UV-Vis spectrophotometer. Taking into ac-
count that dissolution of the complexes in chloroform
was accompanied by their dissociation into initial
components, excess boron trifluoride–ether complex
was added to or gaseous hydrogen chloride was passed
through their solutions to obtain electronic absorption
spectra.
The complex of N-oxide IIb with BF3 was syn-
thesized in a similar way. The N-oxide–BF3 ratio in the
complexes was determined by titration (after prelimi-
nary hydrolysis) as described in [34].
4-Nitropyridine N-oxide hydrochloride. Gaseous
hydrogen chloride was passed through a solution of
0.07 g (0.5 mmol) of 4-nitropyridine N-oxide in 2 ml
of chloroform. The precipitate was separated by
centrifugation and washed with chloroform (3×1 ml).
Yield 0.096 g (92%), colorless powder, mp 128°C.
Found, %: C 34.12; H 3.04; N 15.69. C5H5ClN2O3.
Calculated, %: C 33.98; H 2.85; N 15.92.
The reaction mixtures were analyzed (qualitatively
and quantitatively), and the purity of the products was
checked, by HPLC using a Laboratorni Přistroje chro-
matograph (Praha) equipped with an UV LCD 2040
detector (λ 280 nm for 4-nitropyridine N-oxides or
335 nm for 4-nitroquinoline N-oxides); Separon SGX
C18 column (3×150 mm); eluent acetonitrile–water,
84:16, flow rate 0.2 ml/min. A 0.05-ml portion of the
reaction mixture was placed in a test tube charged with
0.45 ml of a 3% solution of trimethylamine in ethanol,
and a 0.5-μl sample was withdrawn and injected.
A standard reaction mixture contained 0.3 ml of aceto-
nitrile, 0.1 mmol of N-oxide I or II, 0.1 mmol of
Et3BuNCl, and 0.02 ml of BF3· Et2O, 0.02 ml of con-
centrated hydrochloric acid, or 0.1 mmol of solid
π-acceptor III–VI.
N-Oxides Ib–Id hydrochlorides were obtained in
a similar way. In the reactions with N-oxides Ib and
Id, oily substances separated from the solution and
crystallized on storage. The ratio N-oxide–HCl was
determined by titration using Methyl Red as indicator.
REFERENCES
1. Andreev, V.P. and Ryzhakov, A.V., Khim. Geterotsikl.
Soedin., 1999, p. 1443.
2. Ryzhakov, A.V., Vapirov, V.V., and Rodina, L.L.,
N-Oxides Ia–Id, IIa, and IIb were synthesized
according to the procedures described in [17, 18].
Chloroform was purified by standard method [33].
Zh. Org. Khim., 1991, vol. 27, p. 955.
3. Ryzhakov, A.V. and Rodina, L.L., Zh. Org. Khim., 1994,
vol. 30, p. 1417.
4. Andreev, V.P. and Nizhnik, Ya.P., Russ. J. Org. Chem.,
4-Nitropyridine N-oxide complex with BF3.
Boron trifluoride–ether complex, 0.4 ml, was added to
a solution of 280 mg (0.002 mol) of 4-nitropyridine
N-oxide in 6 ml of chloroform. The precipitate was
filtered off, washed with diethyl ether (2×2 ml), and
dried in air. Yield 0.366 g (88%), colorless powder,
mp 143–145°C. Found, %: C 28.79; H 2.06; N 13.71.
C5H4BF3N2O3. Calculated: %: C 28.87; H 1.94;
N 13.53.
2001, vol. 37, p. 141.
5. Andreev, V.P., Ryzhakov, A.V., and Kalistratova, E.G.
Khim. Geterotsikl. Soedin., 1996, p. 516.
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Ward, M.D., J. Am. Chem. Soc., 1998, vol. 120, p. 5887.
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shev, V.V., and Schenk, H., Acta Crystallogr., Sect. C,
2001, vol. 57, p. 397.
Complexes of N-oxides Ib–Id with BF3 were syn-
thesized in a similar way. In the reactions with N-ox-
ides Ib and Id the resulting complexes separated as
oily substances which crystallized on storage.
10. Filippenko, O.S., Chuev, I.I., Leonova, L.S., Shi-
lov, G.V., and Adoshin, S.M., Dokl. Ross. Akad. Nauk,
2001, vol. 376, p. 27.
4-Nitroquinoline N-oxide complex with BF3.
Boron trifluoride–ether complex, 0.4 ml, was added to
a solution of 190 mg (0.001 mol) of 4-nitroquinoline
N-oxide in 5 ml of chloroform, the solvent was dis-
tilled off under reduced pressure, the brown oily
residue was treated with 7 ml of diethyl ether, and the
precipitate was filtered off, washed with 5 ml of di-
ethyl ether, and dried in air. Yield 0.209 g (81%), light
yellow powder, mp 127–131°C. Found, %: C 41.69;
H 2.46; N 10.69. C9H6BF3N2O3. Calculated, %:
C 41.88; H 2.34; N 10.90.
11. Kovalevskii, A.Yu., Ponomarev, I.I., Antipin, M.Yu.,
Ermolenko, I.G., and Shishkin, O.V., Izv. Ross. Akad.
Nauk, Ser. Khim., 2000, p. 68.
12. Yutilov, Yu.M. and Svertilova, I.A., Khim. Geterotsikl.
Soedin., 1994, p. 1071.
13. Andreev, V.P., Nizhnik, Ya.P., Bezruchko, D.G., and
Morozov, A.K., Russ. J. Gen. Chem., 2005, vol. 75,
p. 1309.
14. Baert, F., Schweiss, P., Heger, G., and More, M., J. Mol.
Struct., 1988, vol. 178, p. 29.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 44 No. 12 2008