| Conversions
of perfluoro-substituted 2-amino-4-methylpyrimidines in the oxidation reaction with
potassium permanganate in alkali environment.
L.M Popova, A.Yu.Trishina,S.V. Vershilov Oxidation of 6-perfluorosubstituted 2-amino-4-methylpyrimidines with potassium permanganate in alkali environment has resulted in the formation of the appropriate 2,2'azobis-derivatives of pyrimidines. High cost of fluorine introduction into a molecule is a problem in application of fluorine-containing diazo compounds as potential synthons in production of dyes and biologically active substances. But the unique properties introduced by fluorine, which impossible to attain with the assistance of different elements, contribute to development of organofluorine chemistry, and respective cost reduction of fluorine-containing compounds will allow to expand application area of this class of compounds. To continue investigations in the area of synthesis and
study of properties of derivatives of fluorine-substituted azines and azoles [1,2], we
have carried out the reaction of oxidation of 2-amino-4-methyl-6-perfluoro-substituted
pyrimidines (I-V) with potassium permanganate in alkali environment, as a result
azobis-derivatives of diazines (VI-X)have been separated and described. Earlier the
mentioned 2-amino-pyrimidines (I-V) were reported to be produced by cyclization of
asymmetric fluorine-containing The analysis of literature data [3,4] has shown that introduction of an electron-deficient substituent, perfluorinated fragment in particular, into a dye molecule increases light-resistance and brightness of dyeing. Perfluoroalkyl group as a substituent in a dye molecule
displays strong -I-effect spreading through Azocoupling reactions of various substituted pyrimidines with diazonium salts are widely presented in literature [5]. They are remarkable for variety of reaction conditions affecting the position of azo-group introduction in the pyrimidine ring. It is necessary to remember that diazonium salts react with primary amino groups with formation of diazoamino-products. One of the ways to synthesize azopyrimidines is
diazotization of 2,4,5,6-tetraaminopyrimidines according to standard procedure to
2,4,6-triaminopyrimidyl-5-diazonium chloride following by azocoupling of the intermediate
produced with 2,4,6-triaminopyrimidine in acetate buffer at pH 5.5. As a result of the
reaction, 2,4,6-triamino-5-(2',4',6'-triamino-pyrimidyl)azopyrimidine was yielded in
63%[6]. Attempts to find convenient procedures of separation and purification failed, thus
the formation of azopyrimidine was registered by UV-spectroscopy method. Absorption maxima
in the area of 256,276,390 nm are characteristic for the electron spectra. Appearance of
the absorption bands in the short-wave range of the azopyrimidine spectrum (probably, In the course of the study we synthesized 2,2'-azobis(4-methyl-6-perfluorosubstituted pyrimidines((VI-X) by oxidation of the appropriate 2-amino-derivatives of diazine (I-V) with aqueous-alcoholic solution of potassium permanganate in alkali environment at room temperature for 6 h. Products of azocoupling (V-X) were separated after the reaction mass treatment with 5% solution of hydrochloric acid to pH 4-5 and following extraction with R-113. After distillation of the solvent and drying, the yield of compounds (V-X) attained 60-70%. Perfluoro-substituted azobispyrimidines were separated as viscous oils of a characteristic smell. IR-spectra of 6-perfluorosubstituted azobis-derivatives of pyrimidine (VI-X) presented absorption bands of valence vibrations of methyl groups in a range of 3392-2850cm-1, skeleton vibrations of heteroring are characterized by absorption bands in a range of 1770-1405 cm-1 and valence vibrations of C-F bond become apparent at 1350-890cm-1.
Experimental The IR-spectra were recorded on a Shimadzu IR-470 (Japan) instrument (thin film). Control over the course of the reactions was conducted by thin-layer chromatography method on a Sulifol UV-254 plates. Starting 6-perfluorosubstituted 2-amino-4-methylpyrimidines (I-V) were synthesized according to method[1]. 2,2'-Azobis (4-methyl-6-perfluorohexylpyrimidine)(VI). To a solution of 1.2 g (0.0028 mole) of 2-amino-4-methyl-6-perfluorohexylpyrimidine (I) in 10 mL of ethanol a solution of 0.9g (0.014 mole) of potassium hydroxide in 20 mL of water was added dropwise. A solution of 0.44g (0.0028 mole) of potassium permanganate in 15 mL of water was then added and kept for 4h. The reaction mass was treated with 5%solution of hydrochloric acid to pH 4-5, extracted with R-113, washed with water, dried, the solvent was distilled. The yield was 0.7g (60%), a yellow oily substance. IR spectrum, thin layer (cm-1): 3280,3180,1740,1680,1610,1580,1350,1145. 2,2'-Azobis(4-methyl-6-perfluorooctylpyrimidine)(VII). It was produced similarly to compound (VI) from 2.1g(0.004 mole) of 2-amino-4-methyl-6-perfluorohexylpyrimidine (II). The yield was 1.3g (63%),yellow oily substance. IR-spectrum, thin layer (cm-1):3392,2915,2870,1770,1685,1550,1460,1390-890. 2,2'-Azobis [4-methyl-6-perfluoro(1-methyl-2-oxapentyl)pyrimidine] (VIII).It was synthesized analogously to compound (VI) from 2.0g (0.005 mole) of 2-amino-4-methyl-6-perfluoro(1-methyl-2-oxapentyl)pyrimidine (III). The yield was 1.4g (70%), yellow oily substance. IR spectrum, thin layer (cm-1): 3200,3180, 1680,1620,1540,1440,1300-1280. 2,2'-Azobis[4-methyl-6-perfluoro(1,4-dimethyl-2.5dioxaoctyl)pyrimidine (IX). It was synthesized similarly to compound (VI) from 2.2g (0.004 mole) of 2-amino-4-methyl-6-perfluoro(1,4-dimethyl-2,5-dioxaoctyl)pyrimidine (IV). The yield was 1.4g (65%), light brown oily substance. IR spectrum, thin layer (cm-1): 3390,3120,2910,2850,1680,1590,1440,1340-980. 2,2'-Azobis[4-methyl-6-perfluoro(1,4,7-trimethyl-2,5,8-triundecanyl)pyrimidine] (X). It was synthesized similarly to compound (VI) from 7.3g (0.005 mole) of 2-amino-4-methyl-6-perfluoro(1,4,7-trimethyl-2,5,8-trioxaundecanyl)pyrimidine (V). The yield was 4.47 (60%), oily substance of light-brown color. IR spectrum, thin layer (cm-1): 3392,3110,2900,1769,1683,1405, 1309-995. References:
|
-diketones with
quinidine [1].
-bonds but does not almost show
-R-effect with respect to the electrons of 
-bonds, that is a great
difference in comparison with other electron-deficient substituents such as cyano-group,
nitro-group etc. -R-effect affects brightness of dyeing. More over, fluorine-containing
groups give oleophilicity to dyes, which is the base for development of oil-soluble dyes.