DE1164413B - Process for the preparation of 2-chlorobenzothiazole or 2-chlorobenzoxazole, which are optionally substituted by alkyl or alkoxy groups or by further chlorine atoms - Google Patents

Description

Process for the production of 2-chlorobenzothiazole or 2-chlorobenzoxazole, optionally by alkyl or alkoxy groups or by further chlorine atoms It is known that 2-chlorobenzothiazole can be used with low yields obtained by the action of phosphorus pentachloride on phenyl isothiocyanate.

It is obtained in somewhat better yield by reacting phosphorus pentachloride to 2-mercaptobenzothiazole. 2-chlorobenzothiazole is obtained in an even better yield 2-mercaptobenzothiazole obtained when using sulfur dichloride or disulfur monochloride used as a chlorinating agent. This method is known after another The procedure has been improved by replacing the sulfur dichlorides Sulfuryl chloride used as a chlorinating agent. A big disadvantage when using it of sulfuryl chloride, however, consists in the fact that one is required to achieve good yields necessary excess of sulfuryl chloride must hydrolyze, a measure which difficult to perform in the art and also results in the loss of the excess sulfuryl chloride leads.

It has now been found that 2-chlorobenzothiazole or 2-chlorobenzoxazole, which is optionally substituted by alkyl or alkoxy groups or further chlorine atoms are, more advantageous than obtained by known processes, if one corresponding 2-mercaptobenzazole with phosgene in the presence of inert organic solvents or diluents reacts, the intermediately formed addition products of the mercapto compounds with Phosgene by adding N-substituted carboxamides and / or by heating decomposed and the chlorine compounds formed isolated.

Since it is known from German patent specification 960 279 that one by Conversion of phosgene with mercapto compounds of the imidazole series to diimidazolyl disulfides comes, it was surprising that 2-mercapto compounds of benzothiazoles or benzoxazoles on treatment with phosgene in a simple manner and with good yields in the corresponding Pass over 2-chlorine compounds.

The use of phosgene as a chlorinating agent offers opposite known processes for the preparation of the chlorobenzazoles defined above have the advantage that only gaseous waste products arise, so that the isolation of the process products is particularly easy.

The following can be used as starting materials, for example: 2- mercaptobenzothiazole, 2- mercapto-6-methoxybenzoxazole, 2-mercaptobenzoxazole, 2-mercapto-5-chlorobenzoxazole.

The 2-mercaptobenzazoles are in the presence of inert organic Solvents or diluents reacted with phosgene, preferably in the presence of hydrocarbons, halogenated hydrocarbons or ethers, for example Benzene, toluene, ligroin, chlorobenzene, chloroform, tetrahydrofuran and dioxane.

The reaction can be carried out at room temperature or at elevated temperature, z. B. at the boiling point of the selected solvent.

The 2-mercaptobenzazoles initially form a loose (slightly cleavable) adduct, which in some cases can be isolated, its isolation but is neither necessary nor beneficial.

This intermediate product then breaks down with the release of carbon oxysulphide and hydrogen chloride into the desired chlorine compound. The disintegration of the intermediate product is replaced by N-substituted acid amides, such as dimethylformamide, or dimethylacetamide N-methylpyrrolidone, as catalysts and / or accelerated by heating.

For the example of 2-mercaptobenzothiazole, the reaction can be formulated as follows: 9 / CSH + COC12 t / CSCOC1 j Cl0- only 1 catalyst and / or heat N5; CCl + COS + HCI The compounds obtainable according to the invention are valuable intermediates, e.g. B. for the production of dyes.

In the following examples, parts are parts by weight to understand.

Example 1 Into a mixture of 2000 parts of chloroform 668 parts 2-mercaptobenzothiazole and 3 parts of dimethylformamide are 400 parts of phosgene at 0 ° C initiated. The reaction mixture is stirred at 0 to 10 ° C. for 1 hour and then the temperature was slowly increased to 60 ° C. with the introduction of phosgene Introducing a weak stream of phosgene, the mixture is refluxed for 8 hours. The chloroform is then evaporated off under normal pressure and the residue in vacuo distilled. There are 548 parts (810/0 of theory) of 2-chlorobenzothiazole from the boiling point 141 0C / 30 mm received.

Found .. .. S18.50 / 0, C1 21.0%; calculated for C7H4ClNS. . S 18,900 / 0, Cl 20.910 / 0.

The chloroform is distilled with the interposition of a fractionation column and the residue is distilled in vacuo through an effective fractionating column, in this way the yield can be increased to 595 parts (corresponding to 880/0 of theory).

For comparison, according to the method of the USA. Patent 2469 697, 200 parts of 2-mercaptobenzothiazole within 5 minutes with stirring in 1000 parts of sulfuryl chloride are introduced at 25 "C. The mixture is stirred at 25" C for 1 hour touched. Then ice and water are slowly added until the excess sulfuryl chloride is decomposed. This creates an emulsion. To separate the organic phase the emulsion is mixed with chloroform and the chloroform solution from the aqueous Layer separated. The chloroform solution is first washed neutral with water, then dried with calcium chloride and the chloroform via a packed column distilled off at normal pressure. The residue is in the vacuum of a water pump distilled over.

146 parts (corresponding to 71.80 / 0 of theory) of 2-chlorobenzothiazole are thereby used (Bp 142 "C) obtained.

Example 2 At O "C are in a solution of 99 parts of phosgene and 1 part of dimethylformamide in 500 parts of chloroform 151 parts of 2-mereaptobenzoxazole registered. It is stirred for 1 hour at 0 to 10 ° C. and then slowly while passing in heated to boiling by phosgene. After 8 hours of boiling with the introduction of phosgene the reaction mixture is worked up by distillation. One obtains in 830 / above Yield of 2-chlorobenzoxazole with a boiling point of 105.degree. C./32 mm and a melting point of 4.5.degree.

Found . .. N 9, 130 / o, Cl 22.80 / 0; calculated for C7H4CINO ... N 9.120 / 0, Cl 23.080 / 0.

Claims (1)

Claim: Process for the production of 2-chlorobenzothiazole or 2-chlorobenzoxazole, optionally substituted by alkyl or alkoxy groups or are substituted by further chlorine atoms, d a - characterized in that one corresponding 2-mercaptobenzazole with phosgene in the presence of inert organic solvents or diluents converts, intermediately formed addition products of the mercapto compounds with phosgene decomposed by adding N-substituted carboxamides and / or by heating and the 2-chlorobenzazoles formed isolated. Documents considered: German Patent No. 960 279; U.S. Patent No. 2,469,697.