DE3702671C1 - Process for the preparation of thiocyanatomethylthiobenzothiazole - Google Patents

Abstract

Process for the preparation of thiocyanatomethylthiobenzothiazoles of the formula (I) <IMAGE> in which R is, for example, hydrogen or halogen, by reacting halomethylthiobenzothiazoles of the formula II <IMAGE> in which R has the abovementioned meaning and Hal is halogen, with a thiocyanate of the formula III M<+>SCN<-> in which M<+> is, for example, an alkali metal, in a solid/liquid two-phase system in the presence of known phase-transfer catalysts, characterised in that the molten halomethylthiobenzothiazole as the liquid phase is reacted with the thiocyanate as the solid phase.

Description

The present invention relates to a method for Production of thiocyanatomethylthiobenzothiazoles by Implementation of Halogenmethylthiobenzothiazolen with Thiocyanates.

Synthetic routes for thiocyanatomethylthiobenzothiazoles, the for example used as microbicidal compounds are already known. Corresponding US-PS 35 20 976 are chloromethylthiobenzothiazoles with Metal rhodanide reacted in the presence of organic solvents. When transferring this process to large-scale Scale there are a number of difficulties which are described in more detail in DE-OS 35 04 966.

For example, the organic solvents used recovered and cleaned for ecological reasons become what is detrimental to the economy of the Procedure goes.

It is also known to implement in a two phase system, aqueous solution - solid, in the presence perform a phase transfer catalyst (DE-OS 35 04 966).

The disadvantage of this method is that it is relatively long Response times at elevated temperature and the associated contiguous low space-time yields. The The presence of the water phase in the reaction mixture leads to Accumulation of large quantities of wastewater in high Concentrations contain toxic compounds and not in the natural waters or biological treatment plants may be initiated.

An attempt has now been made to find a method that does not have these disadvantages. Subject of the present Accordingly, the invention is a method for producing Thiocyanatomethylthiobenzothiazolen of the general Formula I,

wherein R is hydrogen, halogen, alkyl having 1 to 6 carbon atoms or trifluoromethyl means by reacting Halomethylthiobenzothiazoles of the general formula II

wherein R has the meanings given above and Hal halogen means with a thiocyanate of the general formula III

M ^⊕ SCN ^⊖ (III)

wherein M ^{⊕ is} an alkali metal or an ammonium ion in a solid-liquid two-phase system in the presence of known phase transfer catalysts, characterized in that the reaction between molten halomethylthiobenzothiazole as the liquid phase and the thiocyanate as the solid phase.

Halogen standing for R can be specified in the general Formulas I and II are fluorine, chlorine or bromine. Chlorine and bromine are preferred, and is particularly preferred Chlorine.

Hal standing for Hal can in the general formula II Chlorine or bromine mean, chlorine being preferred.

The alkyl standing for R in the general formulas I and II can be straight-chain or branched and preferably means C ₁ -C ₃ -alkyl, such as methyl, ethyl, propyl and isopropyl.

Is particularly preferred according to the invention Method 2-chloromethylthiobenzothiazole with ammonium thiocyanate implemented.

To carry out the method according to the invention the corresponding halomethylbenzothiazoles of the general Formula II, especially the corresponding ones 2-chloromethylthiobenzothiazoles with inorganic Thiocyanates of the general formula III normal technical Quality at temperatures at which the halomethylthiobenzothiazole is liquid in the presence of a Phase transfer catalyst implemented.

The reaction mixture is at the reaction temperatures a viscous, but easily miscible mass.

As phase transfer catalysts, for example be used

• a) Crown ethers such as, for example, 18-crown-6, dibenzo-18- Crown-6.
• b) polyethylene glycols or their mono- or diether, such as for example polyethylene glycol 1540, polyethylene glycol monomethyl ether, Polyethylene glycol dimethyl ether, ethoxylated alkylphenols, such as that Commercial product Arkopal® N 100, Arkopal® N 80 etc. or mixtures of the homologous polyethylene glycols, Arkopal® is a registered trademark and Trading product of Hoechst AG),
• c) quaternary onium salts, such as. B. quaternary ammonium or phosphonium salts of the general formula IV R ¹ R ² R ³ R ⁴ A ^⊕ X ^⊖ (IV) where A is nitrogen or phosphorus, R ¹ to R ⁴ independently of one another alkyl, aryl, aralkyl, alkoxyalkyl, each with 1 to 20 C atoms, X is halogen, such as fluorine, chlorine, bromine, iodine, hydrogen sulfate or thiocyanate.

Basically, for the present invention Process all catalysts suitable, the thiocyanate ions in sufficient concentration in the organic Phase can be transferred, so that the above possible phase transfer catalysts only a selection represent. The literature, e.g. B. Dehmlow and Dehmlow, Phase Transfer, Catalysis, Weinheim 1983, names others Examples.

The polyethylene glycols are used for the process according to the invention and their mono- or diether preferred.

In general, the amount according to the invention Process the amounts of the phase transfer catalyst used to 0.1 to 20 wt .-% of the used Halomethylthiobenzothiazole of the formula II. 2 are preferred until 10%. The phase transfer catalysts can be used individually or used in a mixture.

The thiocyanate of formula III can be used in amounts of 1 to 2 mol per mol of the halomethylbenzothiazole of the formula II be used. You bet for economic reasons preferably 1 to 1.2 mol of thiocyanate.

The inventive method is at temperatures at which is the halomethylthiobenzothiazole liquid, the usually means at temperatures between 50 and 110 ° C, preferably at temperatures between 70 and 90 ° C carried out.  

To work up the reaction mixture with a organic solvent in which the inorganic constituents are not soluble, diluted and filtered. A solution of thiocyanatomethylthiobenzothiazole is thus obtained in the solvent. This method is preferred if the phase transfer catalyst in the product may remain and the solvent as a formulation aid can be used for the final formulation can. The presence of a phase transfer catalyst in The end product is often desirable since the end product as a preservative often in aqueous formulations needs to be incorporated and thereby become homogeneous Distribution the addition of an emulsifier is required. With these processes, waste water is avoided, that are difficult to detoxify. Preferred solvents are aromatic hydrocarbons, such as for example toluene, xylenes, trimethylbenzenes and higher Homologue.

The solution of thiocyanatomethylthiobenzothiazole in Aromatic hydrocarbon can continue with others Aids are formulated to be an appropriate one Achieve application form. For example, more Solvents are added, preferably glycol ether, Glycol acetates and glycol esters. Can also with others biocidal active ingredients are combined to cover the spectrum of activity to broaden the thiocyanatomethylthiobenzothiazole. Examples of active ingredients are methylene bisthiocyanate, N-octyl-isothiazolinone-3, benzimidazolyl carbamate etc. called.

But you can also work up the resulting Chloride and the phase transfer catalyst by extraction with water from the thiocyanatomethyltbiobenzothiazole separate when the presence of the phase transfer catalyst is undesirable in use.  

The main advantage of the method according to the invention compared to DOS 35-04-966 is that much higher Space-time yields can be achieved. It also requires that aqueous processes higher reaction temperatures. Also the Addition of organic solvents slows down the reaction considerable and is therefore not practical.

The following examples serve to explain the invention:

Example 1

232 g of 2-chloromethylthiobenzothiazole (content: 91%) together with 91 g ammonium thiocyanate and 20 g Arkopal® N 100 (polyethylene-hoxylated nonylphenol with approx. 10 Ethylene oxide units) heated to 80 ° C for 2 hours. Then it is diluted with 200 g of xylene and the filtered off inorganic salts. The result is a clear one brown liquid.

Yield: 452 g Content: 50% 2-thiocyanatomethylthiobenzothiazole Turnover: 97%

According to example 1, the following compounds are also used produced:

Example 2

232 g of 2-chloromethylthiobenzothiazole (content: 91%) with 117 g of potassium thiocyanate and 10 g of polyethylene glycol 1540 heated to 60 ° C for 8 hours. Then with 200 g of xylene and diluted by filtration from the inorganic Salts separated. The result is a clear brown Solution.

Yield: 428 g Content: 46.8% 2-thiocyanatomethylthiobenzothiazole Turnover: 86%

Example 3

301.8 g of 2-chloromethylthiobenzothiazole (content: 91%) are together with 6 g of triethylbenzylammonium chloride and 102 g of ammonium thiocyanate heated to 80 ° C for 4 hours. Then 300 g of 1,2-dichloroethane and 300 g Water stirred in, the organic phase separated and the solvent up to a bottom temperature of 110 ° C distilled off. There remain 325 g of the brown colored oily 2-thiocyanatomethylthiobenzothiazole back.

Content: 89% Turnover: 95%

Comparative example (Reaction in aqueous medium according to the prior art)

232 g of 2-chloromethylthiobenzothiazole (content: 91%) together with 92 g ammonium thiocyanate, 15 g Arkopal® N 100 and 200 g of water heated to 80 ° C for 2 hours. To The organic product cools down to normal temperature of the aqueous solution of the inorganic salts separated.

Yield: 238 g Content: 37% Turnover: 39%  

After 10 hours at 80 ° C: 90% conversion.

The results obtained show that the space-time Yield much worse than that of the invention Mode of operation fails.

Claims (5)

1. Process for the preparation of thiocyanatomethylthiobenzothiazoles of the general formula I wherein R is hydrogen, halogen, alkyl having 1 to 6 carbon atoms or trifluoromethyl, by reacting halomethylthiobenzothiazoles of the general formula II wherein R has the abovementioned meaning and Hal is halogen, with a thiocyanate of the general formula IIIM ^⊕ SCN ^⊖ (III) wherein M ^{⊕ is} an alkali metal or an ammonium ion, in a solid-liquid two-phase system in the presence of known phase transfer catalysts, characterized in that the reaction takes place between molten Halogenmethylbenzothiazol as the liquid phase and the thiocyanate as a solid phase. 2. The method according to claim 1, characterized in that quaternary onium salts are used as the phase transfer catalyst, Crown ethers and / or polyethylene glycols or their Mono- or Diether uses.   3. The method according to claim 1 and / or 2, characterized in that the phase transfer catalysts in Amounts of 0.1 to 20 wt .-%, based on the amount used Halogenmethylthiobenzothiazol uses. 4. The method according to claims 1 to 3, characterized in that the reaction at temperatures between 50 and 110 ° C, preferably at temperatures between 70 and 90 ° C. 5. The method according to claims 1 to 4, characterized in that the general thiocyanate Formula III in amounts of 1 to 2 mol per mol of Halomethylbenzothiazole of formula II is used.