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Russ.Chem.Bull., Int.Ed., Vol. 58, No. 10, October, 2009
Khisamutdinov et al.
Scheme 3
chloryl fluoride was passed for 1—1.5 h, and the mixture was
poured into cold water (200 mL). In the case of 1c—g and 1i,j,
the heavy viscous oils that formed crystallized on standing, the
resulting crystals were filtered off, washed with water, and dried.
Fluorination of salts 1a,b and 1h resulted in the oily products,
which were extracted with diethyl ether (2×50 mL), the comꢀ
bined organic layer was washed with water (2×50 mL), dried
with MgSO4, and the solvent was removed in vacuo.
The resulting mixtures of 3a—j, 1a—j, and 4a—c were sepaꢀ
rated by column chromatography (silica gel, CH2Cl2—hexane
(1 : 1)).
3: R = Ph (c), pꢀMeOC6H4 (d), pꢀBrC6H4 (e), pꢀO2NC6H4 (f),
mꢀFC6H4 (g)
5: R = Ph (a), pꢀMeOC6H4 (b), pꢀBrC6H4 (c), pꢀO2NC6H4 (d),
mꢀFC6H4 (e)
4ꢀFluoroisoxazoles (general procedure). To a solution of comꢀ
pound 3c—g (0.01 mmol) in MeOH (30 mL), MeONa (0.01 mol,
10% MeONa solution in MeOH) was added and the mixture was
stirred at room temperature for 30 min. The solvent was reꢀ
moved in vacuo, the residue was treated with water, and the
precipitate that formed was filtered off. Recrystallization from
hexane afforded compounds 5a—c and 5e. Compound 5d was
only washed with chloroform.
which were attributed to the fluorine atom bound to the
C(4) atom of the isoxazole ring.
Physicochemical data and the yields of compounds
5a—e are given in Table 2.
In summary, the reaction studied can be regarded as
a convenient preparative synthetic method toward hitherꢀ
to unknown 4ꢀfluoroisoxazoles, which may otherwise be
difficult to obtain.
References
1. L. A. Demina, G. Kh. Khisamutdinov, S. V. Tkachev, A. A.
Fainzil´berg, Zh. Org. Khim., 1979, 15, 735 [J. Org. Chem.
USSR (Engl. Transl.), 1979, 15].
Experimental
2. G. Kh. Khisamutdinov, L. A. Demina, G. E. Cherkasova,
B. G. Klimenko, Zh. Org. Khim., 1979, 15, 2436 [J. Org. Chem.
USSR (Engl. Transl.), 1979, 15].
3. T. V. Trusova, N. G. Maluyta, G. Kh. Khisamutdinov, Zh. Org.
Khim., 1987, 23, 1313 [J. Org. Chem. USSR (Engl. Transl.),
1987, 23].
4. J. P. Freemann, J. Am. Chem. Soc., 1960, 82, 3869.
5. V. Grakauskas, K. Baum, J. Org. Chem., 1968, 33, 3080.
6. F. Ya. Natsibullin, G. V. Oreshko, L. T. Eremenko, Izv. Akad.
Nauk SSSR, Ser. Khim., 1971, 2344 [Bull. Acad. Sci. USSR,
Div. Chem. Sci. (Engl. Transl.), 1971, 20, 2230].
Melting points were determined in capillaries. The IR specꢀ
tra were recorded on a URꢀ20 spectrometer in KBr pellets. The
19F NMR spectra were obtained on a Varian DPꢀ60 instrument
at 56.5 MHz in CDCl3, the chemical shifts are given in the δ
scale relative to CF3COOH as the external standard. TLC was
performed on Silufol UV–254 plates in chloroform—benꢀ
zene (1 : 1).
The starting 4ꢀnitroisoxazolines (1a—j) were synthesized by
the known methods.1
4ꢀFluroꢀ4ꢀnitroisoxazolines 3a—j (general procedure). To
a suspension of compound 1a—g (0.01 mol) in dry MeOH
(14 mL), MeONa (0.01 mol, 10% solution in MeOH) was added
and the mixture was stirred for 1—1.5 h until clear solution was
formed. After the reaction mixture was cooled to 3—5 °C, perꢀ
Received May 20, 2009;
in revised form August 10, 2009