RU2440343C1 - 5-methyl-4-nitrosopyrazoles and synthesis method thereof - Google Patents

Abstract

FIELD: chemistry. ^ SUBSTANCE: 3-methyl-4-nitrosopyrazoles are obtained via cyclocondensation of hydrazine salts with a nitrosation product obtained from 4,4-dimethoxybutan-2-one held in aqueous hydrochloric acid first. The obtained compounds can be used as modifiers and stabilisers of rubber mixtures, particularly during vulcanisation of butadiene-nitrile rubber and as fungicides. ^ EFFECT: novel method of producing 3-methyl-4-nitrosopyrazoles and obtaining novel 3-methyl-4-nitrosopyrazoles. ^ 2 cl, 4 ex

Description

The invention relates to the field of organic chemistry, in particular to 3-methyl-4-nitrosopyrazoles and a method for their preparation, which can be used as compounds having fungicidal activity, and as modifiers and stabilizers of rubber compounds.

There are no analogues of substances. To date, such substances are not known.

Compounds of the 4-nitrosopyrazoles series having methyl (aryl) substituents at the 3 and 5 positions of the pyrazole ring are known.

Known methods to obtain 3-methyl-4-nitrosopyrazoles can not. It was not possible to obtain 3-methyl-4-nitrosopyrazoles by direct nitrosation, despite the fact that electrophilic substitution reactions (for example, halogenation) in pyrazoles proceed easily and the substituent enters position 4, while nitrous acid does not have a significant effect on pyrazoles, and nitroso group in position 4 fails. [Elderfield, Heterocyclic compounds, Moscow: Publishing House of Foreign Literature, 1961. V.5, p.77.]

By cyclocondensation of substituted hydrazines with 3-hydroxyimino-2,4-pentanedione, only 3,5-dimethyl-4-nitrosopyrazoles are obtained, and 3-methyl-4-nitrosopyrazoles cannot be obtained in this way. [US Patent 2,827,415, W.A. Freeman, E. Barnet, D. L. Payne, Rainham, R. Slack. Heterocyclic compounds, claimed 08/13/1956, publ. 03/18/1958.]

Closest to the proposed method for producing 3-methyl-4-nitrosopyrazoles is a method for producing 3,5-dimethyl-4-nitrosopyrazoles structure

where R = cyclopentyl, cyclohexyl, cycloheptyl.

3,5-Dimethyl-4-nitrosopyrazoles are prepared by cyclocondensation of 3-hydroxyimino-2,3-pentanedione with substituted hydrazine salts. In this method of producing 3,5-dimethyl-substituted 4-nitrosopyrazoles, an aqueous solution of 3-hydroxyimino-2,4-pentanedione is added to cycloalkylhydrazine hydrochlorides (cyclopentyl, cyclohexyl, cycloheptyl), then the reaction mass is stirred for 2 hours, the precipitated 3.5 -dimethyl-4-nitrosopyrazole is filtered off.

The disadvantage of this method are:

- Only 1,3-diketone is used for cyclocondensation, namely 3-hydroxyimino-2,4-pentanedione, which is why this method is suitable only for the preparation of pyrazole dimethyl derivatives.

- Only cycloalkanhydrazines are used in cyclocondensation, which does not allow to obtain 3-methyl-4-nitrosopyrazole unsubstituted at the endocyclic nitrogen atom, as well as its phenyl derivative.

According to the known method to obtain 3-methyl-4-nitrosopyrazoles is not possible due to the presence of two methyl groups in 1,3-diketone, which during the reaction form only 3,5-dimethyl-4-nitrosopyrazoles.

There are no analogues of the production method.

The invention solves the single task of creating a new method for producing 3-methyl-4-nitrosopyrazoles.

The technical result consists in creating a new method for producing 3-methyl-4-nitrosopyrazoles and obtaining previously unknown 3-methyl-4-nitrosopyrazoles.

The specified technical result is achieved by the fact that previously unknown 3-methyl-4-nitrosopyrazoles are obtained by cyclocondensation of hydrazine salts of the formula NH ₂ NHR, where R = H, Ph, with the nitrosation product of an aqueous solution of sodium nitrite previously stored in an aqueous solution of hydrochloric acid 4.4 -dimethoxybutane-2-one, with a molar ratio of 4,4-dimethoxybutane-2-one to hydrazine 1: 0.5-1.8.

where R = H, Ph; X = Cl, AcO.

In this way, 3-methyl-4-nitrosopyrazoles were first obtained:

3-methyl-4-nitrosopyrazole

Crystalline substance, blue-green color, T pl. 134-135 ° C (ethanol), ¹ H NMR spectrum (CDCl ₃ ), d, ppm: 2.95 (br s, 3H, CH ₃ ), 7.77 (br s. 1H arom.). ¹³ C NMR Spectrum (CDCl ₃ ), d, ppm: 10.78, 29.81, 161.71. It is soluble in ethanol, chloroform, ethyl acetate, diethyl ether.

3-methyl-4-nitroso-1-phenylpyrazole

Crystalline substance, green, T pl. 106-107 ° C (ethanol), ¹ H NMR spectrum (CDCl ₃ ), d, ppm: 2.70 (br s, 3H, CH ₃ ), 7.43-7.46 (m H arom.), 7.53 -7.55 (m, 2H arom.), 7.77-7.79 (m. 2H arom.), 8.54 (broad s. N arom.). ¹³ C NMR Spectrum (CDCl ₃ ), d, ppm: 12.75, 119.82, 128.45, 129.79, 138.55, 162.44. It is soluble in ethanol, ethyl acetate, chloroform, diethyl ether.

The method of obtaining 3-methyl-4-nitrosopyrazoles is as follows. To 1 N. 4,4-dimethoxybutan-2-one is added to hydrochloric acid, and the reaction mass is stirred for 30 minutes. Then, an aqueous solution of sodium nitrite is added dropwise, nitrogen oxides are blown off. A freshly prepared solution of the salt (acetic or hydrochloric acid) of hydrazine (NH ₂ -NHR, R = H, Ph) is added to the solution of the obtained nitroso compound and stirred for 2-3 hours, at a molar ratio of 4,4-dimethoxybutan-2-one to hydrazine 1: 0.5-1.8 (less or more hydrazine salt leads to a decrease in the yield of target 3-methyl-4-nitrosopyrazoles). 3-Methyl-4-nitrosopyrazoles are isolated by filtration or extraction with an organic solvent.

Example 1. Obtaining 3-methyl-4-nitrosopyrazole.

4,4-Dimethoxybutan-2-one (1.32 g, 10 mmol) is dissolved in 1 N. hydrochloric acid (10 ml), stirred for 30 minutes at 20 ° C, cooled to 0 ° C and a solution of sodium nitrite (0.76 g, 11 mmol) in 4 ml of water was added dropwise over 30 minutes. Nitrogen oxides are blown from the reaction mixture in a vacuum of a water-jet pump, after which a mixture of 10 ml of 1 N hydrochloric acid (10 ml, 10 mmol) and hydrazine hydrate (0.5 ml, 9 mmol). It is stirred for 10 minutes at 20 ° C, the precipitated crystals of blue-green color are filtered off. Yield 0.30 g, 30%. T pl. 134-135 ° C (ethanol). ¹ H NMR spectrum (CDCl ₃ ), d, ppm: 2.95 (br s, 3H, CH ₃ ), 7.77 (br s, 1H arom.). ¹³ C NMR Spectrum (CDCl ₃ ), d, ppm: 10.78, 29.81, 161.71.

Example 2. Obtaining 3-methyl-4-nitrosopyrazole.

4,4-Dimethoxybutan-2-one (1.32 g, 10 mmol) is dissolved in 1 N. hydrochloric acid (10 ml) and stirred for 30 minutes at 20 ° C, then cooled to 0 ° C and a solution of sodium nitrite (0.76 g, 11 mmol) in 4 ml of water was added dropwise over 30 minutes. Nitrogen oxides are blown out of the reaction mixture under a vacuum of a water-jet pump, after which a mixture of acetic acid (1.14 ml, 20 mmol) and hydrazine hydrate (18 mmol) is added. Stirred for 10 minutes at 20 ° C. It is extracted with diethyl ether 5 ml × 5. The extract is dried over sodium sulfate and evaporated. The residue was recrystallized from ethanol. Yield 0.284 g, 28%. T pl. 134-135 ° C (ethanol). ¹ H NMR spectrum (CDCl ₃ ), d, ppm: 2.95 (br s, 3H, CH3), 7.77 (br s, 1H arom.). ¹³ C NMR Spectrum (CDCl ₃ ), d, ppm: 10.78, 29.81, 161.71.

Example 3. Obtaining 3-methyl-4-nitroso-1-phenylpyrazole.

4,4-Dimethoxybutan-2-one (1.32 g, 10 mmol) is dissolved in 1 N. hydrochloric acid (10 ml) is stirred at 30 ° C for 30 minutes, cooled to 0 ° C and a solution of sodium nitrite (0.76 g, 11 mmol) in 4 ml of water is added dropwise over 30 minutes. Nitrogen oxides are blown out of the reaction mixture in a vacuum of a water-jet pump, after which phenylhydrazine hydrochloride (4.5 mmol) in 8 ml of water is added. Stirred for 10 minutes at 20 ° C, the precipitated crystals of green color are filtered off. Yield 66%. T pl. 106-107 ° C (ethanol). ¹ H NMR spectrum (CDCl ₃ ), d, ppm: 2.70 (br s, 3H, CH ₃ ), 7.43-7.46 (m H arom.), 7.53-7.55 (m, 2H arom.) 7.77-7.79 (m, 2H arom.), 8.54 (br. S. N arom.). ¹³ C NMR Spectrum (CDCl ₃ ), d, ppm: 12.75, 119.82, 128.45, 129.79, 138.55, 162.44.

Example 4. Obtaining 3-methyl-4-nitroso-1-phenylpyrazole.

4,4-Dimethoxybutan-2-one (1.32 g, 10 mmol) is dissolved in 1 N. hydrochloric acid (10 ml), stirred for 30 minutes at 20 ° C, cooled to 0 ° C and a solution of sodium nitrite (0.76 g, 11 mmol) in 4 ml of water was added dropwise over 30 minutes. Nitrogen oxides are blown from the reaction mixture in a vacuum of a water-jet pump, after which phenylhydrazine hydrochloride (9 mmol) in 8 ml of water is added. Stirred for 10 minutes at 20 ° C. Extract with chloroform 5 ml × 3. The extract is dried over sodium sulfate and evaporated. The residue was recrystallized from ethanol. Yield 60%. T pl. 106-107 ° C (ethanol). ¹ H NMR spectrum (CDCl ₃ ), d, ppm: 2.70 (br s, 3H, CH ₃ ), 7.43-7.46 (m, H arom.), 7.53-7.55 (m, 2H arom. ), 7.77-7.79 (m. 2H arom.), 8.54 (br. S. N arom.). ¹³ C NMR Spectrum (CDCl ₃ ), d, ppm: 12.75, 119.82, 128.45, 129.79, 138.55, 162.44.

The authors obtained substances not previously described that can find application as compounds having fungicidal activity, and as modifiers and stabilizers of rubber compounds.

Claims (2)

1. 3-Methyl-4-nitrosopyrazoles of the general formula

where R is H, Ph. 2. A method of producing 3-methyl-4-nitrosopyrazoles, comprising cyclocondensation of the nitroso compound and hydrazine salts of the formula NH ₂ NHR, where R is H, Ph, wherein the nitroso compound is the nitrosation product of an aqueous solution of sodium nitrite 4,4-dimethoxybutane-2- it, previously aged in an aqueous solution of hydrochloric acid, with a molar ratio of 4,4-dimethoxybutan-2-one to hydrazine 1: 0.5-1.8.