CS256215B1

CS256215B1 - Process for preparing 2-amino-5-nitrothiobenzamide

Info

Publication number: CS256215B1
Application number: CS867318A
Authority: CS
Inventors: Jiri Kalab; Josef Moravek; Daniela Zlesakova
Original assignee: Jiri Kalab; Josef Moravek; Daniela Zlesakova
Priority date: 1986-10-09
Filing date: 1986-10-09
Publication date: 1988-04-15
Also published as: CS731886A1

Abstract

Způsob přípravy 2-amino-5-nitrothio- Vzorec I benzamidu strukturního vzorce I reakcí 2-amino-5-nitrobenzonitrilu s vodným roztokem sirníku amonného tak, že reakce je prováděna v prostředí dimetylformamidu za přítomnosti amoniaku, který se do reakční směsi přidává v průběhu reakce ve formě 26% vodného roztoku čpavku, přičemž dávkováním sirníku amonného se udržuje teplota v romezí 20 až 25 °C.A method for preparing 2-amino-5-nitrothio-benzamide of structural formula I by reacting 2-amino-5-nitrobenzonitrile with an aqueous solution of ammonium sulfide, such that the reaction is carried out in a dimethylformamide environment in the presence of ammonia, which is added to the reaction mixture during the reaction in the form of a 26% aqueous ammonia solution, while the temperature is maintained in the range of 20 to 25 °C by dosing ammonium sulfide.

Description

, t · 256215

The present invention relates to a process for the preparation of 2-amino-5-nitrothiobenzamide. The preparation of 2-amino-5-nitro-thiobenzamide is described, for example, in Brit. pat. 1 134 579 (Bayer), Belg. pat. 670 652 (BASF), CA 88, 154 310e, in VÚOS 2 464 (Jan. 15, 1982, F. Vyskočil), etc., where it is associated with the reaction of 2-amino-5-nitrobenzonitrile with hydrogen sulfide (rarely with ammonium sulfide) in an environment of ethanol, chloroform, pyridine, isopropanol, resp. 2-ethoxyethanol in the presence of NH 4 or tertiary base (most often triethylamine) as a catalyst. The synthesis of 2-amino-5-nitrothiobenzamide follows the scheme below

2-amino-5-nitrothiobenzamide 2-amino-5-nitrobenzonitrile 2-Amino-5-nitrothiobenzamide is an intermediate for the preparation of 3-amino-5-nitro-2,1-benzisothiazole, i. raw materials for the preparation of high quality dispersion dyes.

It has now been found that 2-amino-5-nitrothiobenzamide is prepared very preferably according to the present invention.

The process of preparing 2-amino-5-nitrothiobenzamide by reacting 2-amino-5-nitrobenzonitrile with an aqueous ammonium sulfide solution according to the invention is characterized in that the reaction is carried out in dimethylformamide in the presence of ammonia, which is added to the reaction mixture as a 26% aqueous solution during the reaction. The ammonia solution and the (NH 4) 2 S reagent are added to maintain the reaction temperature at 20 to 25 ° C.

The synthesis of 2-amino-5-nitrothiobenzamide is carried out by dissolving 2-amino-5-nitrobenzonitrile in dimethylformamide under stirring, and then starting the free aqueous solution of (NH4) 2S. The reaction proceeds immediately and is accompanied by an increase in the reaction mixture temperature, and it is therefore necessary to maintain a temperature in the range of 20 to 25 ° C. After the addition of 1/21 / 2 of sulfonic acid, a portion of 26% aqueous ammonia is added to the reaction mixture to improve the conditions for the redefinition of 2-amino-5-nitrobenzonitrile, and then the remaining amount of ammonium sulfide aqueous solution is added in portions and added. the remaining solution of 26% aqueous ammonia. The progress of the reaction is monitored by chromatography.

After completion of the reaction, the mixture was poured into ice water and the precipitate of 2-amino-5-nitrothiobenzamide was filtered off. The crude product was washed with twice distilled water and dried in a vacuum oven at 80 ° C. Dimethylformamide is recovered from the mother filtrate by distillation. From the aqueous fraction (containing H 2 S) from the distillation of the mother filtrate, hydrogen sulfide is removed in an oxidation column by oxidation of the air at about 80 to 90 ° C and the purified water is discharged into the sewer.

The process used has a number of advantages over the prior art. - Dimethylformamide dissolves 2-amino-5-nitrobenzonitrile practically as the only solvent, but after diluting the reaction mixture with water, the 2-amino-5-nitrothiobenzamide product can be easily separated by filtration, while impurities from 2-amino-5-nitrobenzonitrile (mainly 2,2'-dicyano-4,4'-dinitrodiphenylamine, 2- (2-amino-4-nitrophenyl) -4-amino-6-nitro-benzo [1,3] -diazine and, to a lesser extent, substituted derivatives thereof ) remain dissolved in the parent solution. The dimethylformamide used can be recovered from the mother liquor by simple distillation since it does not form an azeotrope with water. The impurities contained in the distillation residue are disposed of by incineration.

Claims

The use of an aqueous solution of ammonium sulfide is technologically and ecologically more preferred than the use of hydrogen sulfide gas, and the presence of NH 4 is necessary in both cases. A method of disposing of wastewater by removing ammonia after adding NaOH solution is proposed, whereby ammonia is absorbed into the water in the absorption tower and the 2- 2- sulphides in the wastewater are simultaneously converted into S2O3 and SO2 in the oxidation tower. and treated water is discharged into the wastewater. Working with ammonium sulfide at a temperature of about 25 ° C makes it possible to eliminate undesirable reductive effects of ammonium sulfide to the -NO 2 group. At temperatures of 60 ° C or more, the -NO 2 group is already extensively reduced to the -N 2 group. The example below illustrates an embodiment of the invention. EXAMPLE 250 ml of dimethylformamide and 80 g of 2-amino-5-nitrobenzonitrile are introduced into a 1000 ml Keller flask equipped with a stirrer, thermometer, condenser and dosing divider and stirred for 30 minutes at normal temperature. Thereafter, 90 ml of a sulfuric acid solution containing 453 g / l is added to the mixture over about 1 hour and 20 ml of 26% aqueous ammonia are added after about 1 hour. After addition of the aqueous ammonia solution, the remaining 85 mL of the sulfonic acid solution is added to the reaction mixture over about 30 minutes. After stirring the reaction mixture for 1 hour, an additional 20 mL of 26% ammonia solution was added and after 30 minutes of reaction (hexane: ether: acetone / 2: 1: 1 TLC control) the reaction was complete. After completion of the reaction, the reaction mixture was poured into 800 ml of ice-water and the resulting precipitate was filtered through a PDP cloth after stirring for about 15 minutes. The filter cake was washed with 2 x 100 mL cold water and then dried in a vacuum oven at 80 ° C to constant weight. Yield about 86 g, i.e., about 88.9% of theory. The mother filtrate and washings were combined (ca. 1450 mL) and then water and dimethylformamide were distilled off under atmospheric pressure. The dimethylformamide fraction is collected at a temperature of about 153 ° C. Regeneration yields about 185 ml of dimethylformamide. Note: The dimethylformamide fraction can be advantageously collected even at a vacuum of about 30 kPa. The aqueous yellow distillate containing less (NH 4 N 2 S) is aerated with atmospheric air at a temperature of about 80 ° C to 90 ° C after addition of NaOH solution, thereby converting the S, NaHSa and Na 2 S to the appropriate thiosulfates and sulphates, and the effluent in this form The ammonia discharged by the air from the oxidation tower can be recirculated as a water return ammonia back into the process after absorption in the water of the present invention Process for preparing 2-amino-5-nitrothiobenzamide of structural formula csnh2 NHo N ° 2 by reaction of 2-amino-5- nitrobenzonitrile with an aqueous solution of ammonium sulfide characterized in that the reaction is carried out in dimethylformamide in the presence of ammonia, which is added to the reaction mixture as a 26% aqueous ammonia solution during the reaction while maintaining the ammonium sulfide dosage at 20-25 ° C.