JPS5833869B2 - 2 4- Dimethylthiazole - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for producing 2,4-dimethylthiazole, and more specifically, a method for producing 2,4-dimethylthiazole by reacting diisopropylamine and sulfur in a gas phase. The present invention relates to a method for producing 2,4-dimethylthiazole, which comprises forming a carbon film on the inner wall of a reactor in advance.

2,4-Dimethylthiazole is useful as an intermediate raw material for producing active ingredients of agricultural chemicals and medicines.

Conventionally, methods for producing 2,4-dimethylthiazole are known, and a commonly used method includes a method of mixing and heating acetamide, mini-phosphorus sulfide (P2S5), and monochloroacetone to cause ring closure.

This method is described in Organic Synthesis Collective Volume 332-333 (Organic 5
yntheses CoCo11activeVolu
m 332-333 ).

The chemical reaction formula is as follows.

In the known method, the reaction is carried out in a liquid phase, and the yield of 2,4-dimethylthiazole (based on miniphosphorus sulfide) is 41 to 4.
It is about 5%.

However, since this method uses P2S5 as one of the raw materials in the step (1) above, unreacted P2
In recent years, wastewater treatment of S5 and by-product phosphorus compounds has become an important issue.

Therefore, a method that does not use a phosphorus-containing compound as a raw material is desired.

On the other hand, a method using a compound that does not contain phosphorus as a raw material is also known, and in this method, the reaction is carried out in a gas phase, and the chemical reaction formula is as follows.

This method uses easily available and inexpensive diisopropylamine and sulfur as raw materials, and performs a gas phase reaction in a high-temperature reactor.The yield of 2,4-dimethylthiazole (based on diisopropylamine) is approximately 40 to 43%. It is about %.

Moreover, this method allows continuous production and is an advantageous method when implemented industrially.

The present inventors carried out various improvement studies aimed at further improving the yield of the above reaction, and surprisingly found that the reaction was carried out after forming a carbon film on the inner wall of the reactor in advance of the above reaction. It has been found that the yield of 2,4-dimethylthiazole is significantly improved when the method is carried out.

The yield in this case (based on diisopropylamine) is 53~
It was obtained in 59%.

In the method of the present invention, the reactor may be made of either Pyrex glass or stainless steel.

The reaction temperature is preferably about 400 to 550°C, and 400°C
If the temperature is below 550°C, there will be a large amount of unreacted substances, and if the temperature is above 550°C, a large amount of by-products (for example, carbon disulfide, etc.) will be produced.

The reaction time (reactor residence time) can be about 2 to 8 seconds, but 4 to 6 seconds is particularly preferable.

The chemical reaction equivalent ratio of sulfur and diisopropylamine is preferably such that sulfur is slightly in excess, particularly (1,1:1).
~(1,4:1) is preferred.

The reaction is preferably carried out in an inert gas atmosphere, and nitrogen gas, benzene, toluene, hydrogen sulfide, etc. can be used as the carrier gas.

Next, as a method of forming a carbon film on the inner wall of the reactor in advance of the above reaction, a hydrocarbon such as n-hexane or toluene and sulfur (or oxygen) are introduced into the reactor, and 400 to 500 Mix and dehydrogenate at °C,
A method in which a carbon film is formed is preferred, and the reaction is then carried out by immediately switching the supply of hydrocarbon to the supply of diisopropylamine.

2,4-dimethylthiazole in the reaction product can be easily separated by distillation.

This compound has been confirmed to be 2,4-dimethylthiazole because its gas chromatography, mass spectrometry, and infrared spectrum are identical to the standard material synthesized by the method described in the above-mentioned document.

Next, comparative examples and examples will be specifically described, but the present invention is not limited only to these examples.

Comparative Example 1 955 P/h of diisopropylamine and 4017 h of nitrogen gas were introduced into a vaporizer temperature controlled at 400° C. to form a mixed gas stream, while 1574 P/h of sulfur (1.3 times the chemical reaction relative to diisopropylamine) (equivalent) and nitrogen gas 401/hour are introduced into a vaporizer whose temperature is controlled at 580° C. to form a mixed gas stream, and these two mixed gas streams are introduced into a reactor made of Pyrex glass for a mixing reaction.

The reaction was carried out for about 1 hour at a reaction temperature of 450° C. and a reaction time of 4 seconds.

As a result of collecting a part of this reaction product and quantitatively analyzing it by gas chromatography, it was found that the yield of 2,4-dimethylthiazole was 4.
Yield 41.0% at 38r (based on diisopropylamine)
was gotten.

The measurement conditions for gas chromatography are as follows.

Gas chromatograph 5, filler (7) type: GC-4AH type (manufactured by Shimadzu Corporation) Column length: 3 m Column temperature: 140°C Kajika packing material, polyethylene glycol 20% by weight
(Carrier: Celite 545) Carrier gas: Helium Carrier gas pressure: 1 kg/crAG Example 1 n-hexane 700? /h and nitrogen gas 401/h were introduced into a vaporizer temperature-controlled at 400°C to form a mixed gas stream, while sulfur 520 f/h (2.0 moles relative to n-hexane) and nitrogen gas 4017 h 5
A mixed gas stream is introduced into a vaporizer temperature-controlled at 80°C, and these two mixed gas streams are heated using stainless steel (
Introduced into a reactor made of SUS27) and mixed, 450 to 500
A carbon film was formed on the inner wall of the reactor by flowing the mixture for about 30 minutes with a residence time of 10 seconds through the reactor maintained at a temperature of .degree.

Next, the supply of n-hexane was stopped, and the supply of diisofurobilamine was switched to carry out the reaction.

The reaction conditions were exactly the same as in Comparative Example 1 except that the material of the reactor was different.

The product was identified according to Comparative Example 1.

Yield of 2,4-dimethylthiazole: 630P, yield: 59
．． 0% was obtained.

Example 2.3.4 Using the same equipment as in Example 1 and using the same method, the reaction temperature,
The reaction was carried out by changing the reaction time and the chemical reaction equivalent ratio of sulfur and diisopropylamine.

Identification of 2,4-dimethylthiazole was performed according to Example 1.

The results are shown in Table 1 together with the results of Example 1.

The method of the present invention has the following advantages over the conventional method for producing 2,4-dimethylthiazole.

(1) Raw materials are easily available and relatively inexpensive.

(2) High yield and good quality.

(3) It is a gas phase reaction and the reaction time is short.

(4) It is possible to manufacture continuously.

(5) Since compounds containing phosphorus are not used as raw materials, no wastewater treatment or recovery process is required.

As described above, the method of the present invention is extremely advantageous when implemented economically on an industrial scale.

Claims (1)

[Claims] 1 2,4-dimethyl characterized by forming a carbon film on the inner wall of the reactor in advance when producing 2,4-dimethylthiazole by reacting diisopropylamine and sulfur in a gas phase. Method for producing thiazole.