DD277679A1 - PROCESS FOR THE THERMOLYTIC MANUFACTURE OF NEW 4- (ARYL-AMINO) -5,7-DINITROBENZOFURAZANES - Google Patents

Abstract

The invention relates to a process for the preparation of novel 4- (N-arylamino) -5,7-dinitrobenzofurazans of general formula I, which are obtained according to the invention in a simple manner by a thermolytic route, preferably by heating alkali metal 4- (N-) formyl-N-aryl-amino) -5,7-dinitro-4, x-dihydrobenzofurazanide-3-oxide in water. The new compounds are useful as intermediates for dyes, rubber antifriction agents or biologically active compounds. Formula I

Description

Field of application of the invention

The invention relates to a process for the preparation of novel 4- (N-arylamino) -5,7-dinitrobenzofurazans which are useful as dye intermediates, rubber anti-precursor precursors or as intermediates for biologically active substances.

Characterization of the known prior art

Of the possible amino derivatives of 4,6-dinitrobenzofurazane, only the 4-amino-5,7-dinitrobenzofurazane is known, the synthesis of which is preferably carried out from the 4-chloro-5,7-dinitrobenzofurazane with gaseous ammonia (SU-PS 627129, Chem. Abstr. 90 119791 , P 23063v) or from 4,6-dinitrobenzofurazan with hydroxylamine hydrochloride in ethanolic potassium hydroxide solution (SU-PS 745301, Chem. Abstr. 94 (19811, P 84128z) takes place.

Also known is the nitration of 4-amino-7-nitrobenzofurazane (Tetrahedron 2411968], 6145), which is accessible only in very low yield from the 4-chloro-7-nitrobenzofurazan (J. prakt. Chem. 32711985), 487th ; J. Med. Chem. 1111968], 305; J.

Chom. Soc. B. 1966, 2004).

As a possible potential Vorprodukto for the new 4- (N-arylamino) -5,7-dinitrobenzofurazane would be the 4-Halogennitrobenzofurazane conceivable, but accessible only after several synthetic steps with a low overall yield

90 (1979), P 23063v, SU-PS 657025, Chem.Abstract 9111979], P 20519h, SU-PS 10043/5, Chem. Abstr.99 [1983], P-70706c, SU-PS '006434, Chem.Abstr.98 [1983], P 88201 n; SU-PS 937454, Chem. Abstr.97 [1982], P 198206r; DD-PS 137100; DD-PS 2Ot ⁴ SSe ).

Object of the invention

The aim of the invention is to develop a process for the preparation of novel 4- (N-aryl-ai.iino) -5,7-dinitrobenzofurazans.

Explanation of the essence of the invention

The object of the invention is to prepare starting from readily available precursors based on 4,6-dinitrobenzofuroxan new 4- (N-aryl-amino) -5,7-dinitrobenzofurazane.

This object is achieved by a process for the preparation of novel 4- (N-aryl-amino) -5,7-dinitrobenzofurazans of general formula I,

in the

R is hydrogen, an alkyl, alkoxy, halogen, dialkylamino or a nitro radical, by according to the invention a Meisenheimerkomplex of the general formula II,

in the

M ^{f represents} a metal cation, preferably sodium or potassium, and

R has the meaning given above,

in a suitable reaction medium at temperatures between 30 and 15O ⁰ C subjected to a thermolysis. Preferably, this reaction is carried out in water at temperatures between 50 and 100 ⁰ C.

As the thermolysis medium, instead of water, organic solvents such as toluene or xylene may also be used, the temperature of the thermolysis being limited by the boiling point of the solvent. In these cases, it is necessary to remove the alkali formate formed during the reaction from the reaction mixture by extraction methods, provided that the 4- (N-arylamino) -5,7-dinitrobenzofurazane is sparingly soluble in the organic phases. If, on the other hand, water is used as the thermolysis medium, then the alkali formates remain in solution. The target products are also insoluble in hot water. The use of water also has the advantage that the risk of safety in dealing with the explosive Meisenheimerkomplexen dinitrobenzofuroxan is minimized. The alkali metal 4- (N-formyl-N-arylamino) -5,7-dinitro-4, x-dihydrobenzofurazanide-3-oxides required for the reaction are prepared by reacting 4,6-dinitrobenzofuroxan with the alkali metal salt of formanilides easily accessible.

In some cases, 4- (N-arylamino) -5,7-dinitrobenzofurazme are by-products of synthesis of the Meisenheimerkomplexe. This is always observed when working at reaction temperatures above 30 ⁰ C. In diosome case, the 4- (N-aryl-amino) -5,7-dinitrobenzofurazane remain in the organic phase, if tetrahydrofuran is used as solvent. The target products are obtained in high purity by concentration of the solvent and subsequent cooling.

After the solution according to the invention new 4- (N-aryl-amino) -5,7-dinitrobenzofurazane be obtained in a simple procedure from readily available precursors and in guton yields.

The state of the art enriching advantage of the solution according to the invention is that starting from readily available precursors and arrives in oinom step to the target products.

The structures of the compounds obtained were clearly characterized by ¹ H and 13 C NMR studies.

embodiments example 1

4-LN- (4-Methoxyphenyl) amino) -5,7-dinilrobenzofurazan

Potassium formanisidide (3.78 g, 20.00 mmol) is finely suspended in tetrahydrofuran (50 mL) using ultrasound (40KHz, 50W). A solution of 4,6-dinitrobenzofuroxan (5.00 g, 22.12 mmol) in tetrahydrofuran (50 ml) is added dropwise to this suspension over a period of 20 minutes, while cooling with cold water, while maintaining the ultrasound dispersion.

After a further 45 minutes, diethyl ether (50 ml) is added and the reaction mixture allowed to stand at room temperature for 2 hours. The red-brown precipitate is filtered off with suction, washed with tetrahydrofuran / diethyl ether and dried in air. This gives 6.23 g (75% of theory) of potassium 4- [N-formyl-N- (4-methoxyphenyl) amino] -5,7-dinitro-4, x-dihydrobenzofurazanide 3-oxide with a decomposition point of 178 18O ⁰ C.

The mother liquor of the reaction mixture is concentrated to dryness and the residue is brought into solution with just a sufficient amount of acetone. With water, it falls 1.35 g of mitgebildeten 4- [N- (4-methoxyphenyl) amino | -5,7-dinitrobenzofurazans from (m.p. 245 to 248 ⁰ C.).

6,23g (15,00mmo!) Of the Meisenheimerkomplexes shown above are suspended in 50ml of water and kept under stirring for 2 hours at a temperature of 90 to 100 ⁰ C, wherein the reddish brown complex salt dissolves and from the hot solution an orange precipitate fails. It is cooled to 0 to 5 ⁰ C, filtered off with suction and the residue is washed with water. After drying, 3.50 g of 4- [N- (4-metiioxyphenyl) amino] -5,7-dinitrobenzofurazan, mp. 247 to 248 ⁰ C.

Analysis (C ₃ H ₉ N ₅ O ₆ ):

calc .: C 47.13; H 2,74; N 21.14%

Found: C 47.34; H 2.91; N 21.24% overall yield: 4.85 g (73% of theory, based on potassium formanisidide used).

Example 2

4- (N-phenyl-amino) -5,7-dinitrobenzofurazan

A solution of 4,6-dinitrobenzofuroxan (11.30 g, 0.05 mol) in 100 ml of absolute tetrahydrofuran is added dropwise to a suspension of sodium formanilide (7.15 g, 0.05 mol) in 100 ml of absolute toluene with stirring over 5 to 10 minutes added. The reaction is slightly exothermic and a dark brown suspension forms. Subsequently, the reaction mixture is heated to reflux of the solvent mixture (about 80 to 85 ⁰ C) and stirred for 4 hours at this temperature. The resulting orange-red colored solution is filtered after cooling. The filter residue is washed twice with 50 ml of tetrahydrofuran, the filtrates combined and concentrated together with the mother liquor to a total volume of about 50 ml. After cooling this mother liquor is filtered off with suction, the precipitated 4- (N-phenyl-amino) -5,7-dinitrobonzofurazan, washed with diethyl ether and dried in air.

Yield: 8.40 g (56% of theory); Mp. 243 to 246 ° C.

Potassium formanilide (2.07 g, 13.00 mmol) is finely suspended in absolute tetrahydrofuran (25 mL) and then portionwise with stirring with a solution of 4,6-dinitrobenzofuroxan (3.00 g, 13.27 mmol) in absolute tetrahydrofuran (25 mL). added, wherein the temperature of the reaction mixture by occasional cooling at about 10 ° C holds. After the reaction has subsided, 20 ml of diethyl ether are added and the mixture is allowed to stand at room temperature for several hours.

Subsequently, a further 20 ml of diethyl ether are added together with 10 ml of pentane and then the reaction mixture is cooled to about ⁰ ° C.

The precipitated product is filtered off with suction and washed with tetrahydrofuran / diethyl ether / pentane (1: 2: 1, 30 ml). The potassium 4- (N -formyl-N-phenylamino) -5,7-dinitro-4, x-dihydrobenzofurazanide-3-oxide (4.15 g) is obtained as an ocher-brown powder.

The mother liquor is concentrated to dryness and the dark red residue is taken up in a little acetone (about 10 ml).

After precipitation with water is obtained from it 0.38 g of 4- (N-phenyl-amino) -5,7-dinitrobenzofurazan.

The separated Meisenheimerkomplex is mixed with 50 ml of water and heated with stirring for 30 minutes at about 90 ° C.

It is then cooled and sucks the deposited orange-colored product (2.43 g, mp 247 to 248 ⁰ C) from.

Total yield: 2.81 g (72% of theory, based on potassium formanilide); Mp .: 248 to 249 ⁰ C (from THF).

Analysis (C ₁₂ H ₇ N ₅ O ₆ ):

calc .: C, 47.85; H, 2.34; N 23.25%

found: C, 47.88; H 2,13; N 22.89%.

Example 3

4- | N- (4-N, N-dimethylaminophenyl) amino | -5,7-dinitrobenzofurazan

5.0 g (12.13 mmol) of sodium 4- (N-formyl-N- (4-N, N-dimethylaminophenyl) amino-5,7-dinitro-4, x-dihydrobenzofurazanide-3-oxide, which is prepared from 4,6-Dinitrobonzofuroxan (15.33 mmol) and Dorstöchiometrischen Monge sodium 4-N, N-dimethylaminoformanilid hoistollt is stirred in 100ml Wassor oino Stundo at 80 ⁰ C. The color of the mixture changes rapidly, and it falls oin The product is filtered off with suction and the crude product is purified by reprecipitation from dimethylformamide with addition of water

 Boutoute: 3.92g; M. 257 "C

C ₁₄ H ₁ JN ₆ O ₆ ):

boron: C, 48.84; H 3.51; N 24.41%

gof .: C, 48.81; H 3.56; N 23.84%.

Example 4

4- [N- (2 "ethylphenyl) amino] -5,7-dinitrobenzofurazan ₁ O ₁ Og (25.19 mmol) sodium 4- [N -forynyl-N- (2-ethylphenyl) amino] -5,7-dinitro -4, x-dihydrobenzofurazanide-3-oxide are stirred in 200 ml of boiling water for about one hour. The deposited yellow crude product is filtered off, dried in air and 300ml of toluene / dimethylformamide (2: 1) under addition of petroleum (bp 80 to 100 ⁰ C.) And reprecipitated.

Yield: 7.34 g (89% of theory, based on the used Meisenheimerkomplex); M.p. 260 ° C.

Analysis (C ₁₄ H ₁₁ N ₅ O ₅ ):

calc .: C, 51.06; H 3.37; N 21.27% Found: C 51.11; H 3.36; N 20.86%.

Claims (4)

1. A process for the preparation of novel 4- (N-arylamino) -5,7-dinitrobenzofurazans of general formula I, in the R is hydrogen, an alkyl, alkoxy, halogen, dialkylamino or a nitro radical, characterized in that a meisenheimer complex of the general formula II, in the M + represents a metal cation and R has the meaning given above, in a suitable reaction medium at temperatures between 30 and 150 ⁰ C is subjected to a thermolysis. 2. The method according to claim 1, characterized in that one uses for the Thermolysereaktion the sodium or potassium salts of Meisenheimerkomplexe. 3. The method according to claim 1 and 2, characterized in that the thermolysis is carried out in water. 4. The method according to claim 1 and 2, characterized in that an organic solvent is used as the thermolysis medium.