DE1171420B - Process for the preparation of aromatic diisothiocyanates - Google Patents

Description

Process for the preparation of aromatic diisothiocyanates It is already known that phenylenediisothiocyanate- (1,4) can be obtained by the reaction of phenylenediamine (1,4) with thiophosgene (see reports of the German Chemical Society, Vol. 20 [1887], p. 230), by cleavage of polymeric p-phenylenethiourea with acetic anhydride (see Journal American Chemical Society, Vol. 45 [1923], p. 2354) or by conversion of the diammonium salt of phenylene-bis-dithiocarbamic acid with iron salts (cf. German patent specification 700 436) can win. However, the aforementioned procedures are little for the production of aromatic diisothiocyanates on an industrial scale suitable.

There are also processes for the conversion of aromatic monoamines known in monoisothiocyanates (cf.H 0 U b e n - W e y 1, Methods of Org.Chemistry, 4th edition, Vol. 9, pp. 867ff.), Which, however, do not automatically relate to the series let the diisothiocyanate transfer. The yields of the last-mentioned compounds are usually only very low, as the monoisothiocyanates owing to their poor solubility fail and are thus withdrawn from further implementation.

Finally it is known from German patent specification 960 276, isothiocyanates by preparing N-monosubstituted dithiocarbaminates with chlorites, in particular sodium chlorite in an aqueous medium with the addition of organic solvents implements. However, this process fails in the production of aromatic diisothiocyanates.

So could when working according to Example 1 of the patent mentioned The only difference is that diaminonaphthalene (1.4) is used instead of n-butylammine was, the desired naphthylenediisothiocyanate- (1,4) only in 2.50 /, iger yield can be obtained.

Similarly, in the preparation of diphenylene diisothiocyanate (4,4 ') only achieved a yield of 2.3 0 / o.

It has now been found that isothiocyanates can be obtained by reacting Dithiocarbaminates can be produced with alkali metal chlorites by the fact that for production of aromatic diisothiocyanates salts of aromatic bisdithiocarbamic acids in aqueous phase free of organic solvents and exposed to the action of alkali chlorites subject.

Aromatic ones are used as starting materials for the process according to the invention Bis-dithiocarbamates with one or more rings are considered, the individual Rings can be bonded or fused to one another directly or via alkylene groups. Typical representatives of these compounds are z. B.

Phenylene and naphthylene bis-dithiocarbamates, diphenylene bis-dithiocarbamates as well as arylene bis-dithiocarbamates substituted by halogen, alkoxy groups or alkyl radicals, z. B. 2-chloro, 2-methoxy, 2,6-dichloro and 2,5-dimethylphenylene-bis-dithiocarbamates called.

The compounds coming into consideration as starting materials can z. B. be produced according to the method according to patent 1 134063 in the way, that one dissolves aromatic primary diamines in dimethylformamide, with ammonia and carbon disulfide converts and the ammonium salts thus obtained, optionally into other base salts convicted.

Except for the manufacturing method specified above directly accumulating ammonium salts can also contain other base salts such as substituted ammonium salts, z. B. triethylammonium salts, and alkali salts, especially sodium and potassium salts can be used. Alkali metal chlorites are preferably used as the reaction component Sodium or potassium chlorite into consideration.

To carry out the method according to the invention, one proceeds appropriately in such a way that one is in the aqueous, organic solvent-free solution of a salt of the abovementioned bisdithiocarbamic acids, an aqueous solution of a Allow alkali chlorite to run in with stirring. It is useful to have a concentrated Chlorite solution, e.g. B. to use a 20- to 400% solution. The resulting Precipitate is separated off and the diisothiocyanate obtained is dried. This The product is already of great purity. If desired, it can be used for further cleaning dissolved in methyl formate, the solution clarified and until crystallization be narrowed.

The process gives the diisothiocyanates in good to very good quality Yields which naturally depend on the reaction conditions used are. One has proven to be particularly useful Working at temperatures between - 15 and + 30 ° C, preferably between -5 and t12 "C.

Although the implementation according to the invention also with the calculated amount Chlorite can be carried out, better results are achieved if one Excess thereof, preferably 2 to 3 moles, applies.

When dissolving the process products from methyl formate it is advantageous to use a clarifying agent, e.g. B. decolorizing carbon or activated carbon, with to use.

Compared to the known methods of production mentioned at the beginning of diisothiocyanates, the present process is characterized in that it in almost quantitative yield to pure, directly usable in veterinary medicine Products. For use in human medicine, further cleaning can be done of the process products with the aid of methyl formate is sometimes recommended be.

The process products are characterized by their effectiveness against numerous species from the families of hookworms, tapeworms, roundworms and nodule worms as well as their low toxicity. You can, if necessary, after transfer used in suitable pharmaceutical preparations for combating parasitic helminths will.

Example 1 Phenylene diisothiocyanate (1.4) 586.8 g (1 mole) diammonium salt the phenylene bisdithiocarbamic acid (1,4), containing 4 moles of crystal dimethylformamide, are dissolved in 4000 cm9 of distilled water. Then one leaves below at +10 "C. Stirring 520 cm3 of a 35% aqueous sodium chlorite solution run in. The educated The precipitate is then separated off by centrifugation and washed with water and spun dry.

The obtained phenylene diisothiocyanate (1,4) is in the vacuum drying cabinet dried at 400 C, dissolved in methyl formate, the solution filtered, with Clarified coal and concentrated the resulting filtrate until crystallization. Man 175 g (91% of theory) of pure phenylenediisothiocyanate are obtained in this way. The melting point of the preparation is 130 "C.

Analysis: C8H4N2S2 (192.5).

Calculated . . . C 49.98, H 2.10, N 14.57, S 33.35 ° / 0; found ... C 50.01, H 2.21, N 14.39, S 33.44O / o.

The same yield of a product of the same purity is obtained if you start from a diammonium salt of phyenlenebis-dithiocarbamic acid, which is free from crystal dimethylformamide.

Analogously to Example 1, the diammonium salts of the phenylene - bis - dithiocarbamic acid - (1,3) phenylenediisothiocyanate- (1,3) of m.p. 53 "C, the 2-chlorophenylene-bis-dithiocarbamic acid- (1,4) 24-chlorophenylene diisothiocyanate- (1,4) from 59 to 60 ° C. of 2-methoxyphenylenebis-dithiocarbamic acid- (1,4) 2-methoxyphenylenediisothiocyanate- ( 1.4) at 100 ° C, the 2,6-dichlorophenylene-bis-dithiocarbamic acid- (1,4) 2,6-dichlorophenylene diisothiocyanate - (1,4) and the 2,5 - dimethylphenylene - bis - dithiocarbamic acid - (1,4) 2,5-dimethylphenylenediisothiocyanate- (1,4) obtained from the mp 107 to 1100C in yields between 90 and 950 /, the theory.

Example 2 Naphthylenediisothiocyanate- (1,4) Analogously to Example 1 are used 63.7 g (1/1 mole) of the diammonium salt of naphthylene-bis-dithiocarbamic acid- (1,4), containing 4 / mol of crystal dimethylformamide, in aqueous solution with 2 / ,, mol of a 350% strength sodium chlorite solution reacted at 0 ° C.

From methyl formate, 22.5 g (93% of theory) are pure crystallized naphthylenediisothiocyanate- (1,4) of melting point 122 "C.

Analysis: Cl2H6N2S2 (242.30).

Calculated ... C 59.48, H 2.50, N 11.56, S 26.46 ° / o; found ... C 59.61, H 2.63, N 11.59, S 26.66 O / o.

The same yield of a product of the same purity is obtained if one of a diammonium salt of naphthylene-bis-dithiocarbamic acid- (1,4) starts out, which is free of crystal dimethylformamide.

Example 3 Diphenylenediisothiocyanate- (4,4 ') By reacting a aqueous solution of 51.7 g (1/1 in mol) of the diammonium salt of diphenylenebis-dithiocarbamic acid - (4,4 ') containing 510 moles of crystal dimethylformamide, in 1000 cm3 of distilled Water with 65 cm3 of a 350/0 strength aqueous sodium chlorite solution at +5 ° C becomes a light gray precipitate obtained. After purification as in Example 1, 24.2 is obtained g (90% of theory) crystallized diphenylenediisothiocyanate (4,4 '). The substance melts at 205 "C.

Analysis: C14H8N2S2 (268.34).

Calculated ... C 62.66, H 3.00, N 10.44, S 23.90 ° / o; found .. C 62.53, H 3.05, N 10.71, S 24.02 ° / o.

The same yield of a product of the same purity is obtained if one of a diammonium salt of diphenylene-bis-dithiocarbamic acid- (4,4 ') starts out, which is free of crystal dimethylformamide.

Claims (2)

Claims: 1. Process for the production of isothiocyanates by reacting dithiocarbaminates with alkali chlorites, d a d u r c h gek e n n z e i n e t that one can produce aromatic diisothiocyanates Salts of bis-dithiocarbamic acids in aqueous, organic solvents free Phase subjected to the action of alkali chlorites. 2. The method according to claim 1, characterized in that the Implementation at temperatures between -15 and +300 C, preferably between -5 and +12 "C. Documents considered: German Patent No. 960 276.