JPS62161773A - Production of 2-chlorobenzothiazole compound - Google Patents

Abstract

PURPOSE:To produce the titled substance useful as an intermediate raw material for pharmaceuticals and agricultural chemicals at a low cost with little produc tion of industrial wastes, by reacting a mixture of a 2-mercaptobenzothiazole compound and solid sulfur with chlorine in the presence or absence of an organic solvent. CONSTITUTION:A 2-mercaptobenzothiazole compound of formula I (R is methyl, halogen or H) and solid sulfur are made to react with chlorine by solid-vapor reaction or in a state suspended or dissolved in an organic solvent. After completion of the reaction, by-produced hydrogen chloride and produced unreacted sulfur chloride are neutralized with dilute alkali and separated and removed as precipitated sulfur. 2-Chlorobenzothiazole attached to the separated sulfur or dispersed in the neutralization water can be extracted and separated in high efficiency by the addition of an organic solvent (e.g. benzene) having low compatibility with water. The separated sulfur can be reused.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to a novel method for producing 2-chlorobenzothiazoles.

More specifically, formula (1) [wherein R represents any one of a methyl group, a halogen group, and a hydrogen atom]. A mixture of 2-mercaptobenzothiazoles and solid sulfur represented by the formula (II) is reacted with chlorine in the presence or absence of an organic solvent, and )10 Represents either a gen group or a hydrogen atom. The present invention relates to a method for industrially and economically producing 2-chlorobenzothiazoles represented by the following formula. 2-Chlorbenzothiazole has a highly reactive chlorine atom at the 2-position, and is an important compound as an intermediate raw material for pharmaceuticals and agricultural chemicals such as plant protection agents.

(b) Prior Art Conventionally, methods for producing 2-chlorobenzothiazole include: 1) A method of heating 2-mercaptobenzothiazole with phosphorus pentachloride and oxine phosphorus chloride. (Nishizou Takahashi, Heizo Taniyama, Pharmaceutical Science Magazine 67, 42 (1947')) 2)
, a method of reacting phenyl isocyanate with phosphorus pentachloride. (Daikoku Kauke Vol. 15 P, 152. Supervised by Mujio Kotake, Asakura Shoten, (1958)) 3) A method of causing sulfuryl chloride to act on 2-mercaptobenzothiazoles. (Chemical, Abstract, 61. 4174
”) 4), Method of heating 2-mercaptobenzothiazole and sulfur monochloride (G, W. Watt, Journal, Off. Organ Chemistry (J, Org.).

chem, )4, 436 (1c+3c+)) The above methods are known. However, it has the following drawbacks in economically producing 2-chlorobenzothiazole on an industrial scale.

That is, in any of the methods 1) to 3), the raw materials are expensive and the handling of the raw materials V) is difficult, so they cannot be used as industrial production methods.

Regarding 4), the manufacturing method uses relatively inexpensive raw materials;
Although industrialization is possible, the yield is poor and the raw material, sulfur monochloride, has poor storage stability and a bad odor.

It is a compound with a pungent odor and is difficult to handle.

(c) Problems to be Solved by the Invention Can 2-chlorobenzothiazole be solved using the above conventional method? When manufacturing,
After the reaction is completed, in addition to the target product 2-chlorobenzothiazole, a highly viscous tar substance containing hydrogen chloride, sulfur, sulfur chloride, and a benzothiazole-based polymer homogeneous substance is found in the reaction mixture. include. In this state 2
- If chlorobenzothiazole is subjected to distillation purification, the decomposition of 2-chlorobenzothiazole will be accelerated during distillation, resulting in a decrease in yield and purity of the product, making it difficult to handle.
1. A large amount of foul-smelling waste will be produced as a by-product, resulting in environmental pollution and the burden of pollution treatment costs.

(c) Structure of the invention In order to overcome the above-mentioned industrial drawbacks, the present inventors have
As a result of extensive research, we have discovered an industrially and economically viable method for producing 2-chlorobenzothiazole, resulting in the present invention.

That is, in the presence of 2-mercaptobenzothiazole and inexpensive solid sulfur, chlorine is introduced at room temperature or with heating, and the reaction is carried out in a solid-gas reaction or in a suspended or dissolved state in an organic solvent. It is something to do. This is achieved by synthesizing active 5XC12 in the reaction system and immediately reacting it with 2-mercaptobenzothiazole.
-Chlorbenzothiazole is estimated to be produced in good overall yield.

In addition, in the method for producing 2-chlorobenzothiazole, in order to achieve a high finality and a good yield, in order to minimize the amount of waste after removal, neutralization using alkali bicarbonate after the reaction is performed. , precipitated as sulfur,
Separate and remove. Furthermore, 2-chlorobenzothiazole adhering to the separated sulfur and turbidity in the neutralized water cause Vl
In order to remove 2-chlorobenzothiazole, Vh that is compatible with water or H that is slightly miscible vs. organic solvents, such as benzene, toluene, xylene,
Chloroform.

By adding dichloroethane, dichloromethane, etc., 2-chlorobenzothiazole can be efficiently extracted and separated into the organic layer. The extraction solvent can also be added in advance at the start of the reaction to allow the reaction to proceed.

By carrying out the above operations, the sulfur dissolved in the tar-like substance is precipitated as a solid and separated and removed.

Next, the organic solvent in the organic layer is recovered by distillation, and V), which is vacuum distilled, is recrystallized to obtain 2-chlorobenzothiazole, which is the target product.

Furthermore, the separated and removed solid sulfur can be reused as raw material sulfur in the next reaction, and even if it is repeatedly reused, it will not affect the purity or yield of the product in any way. It can be significantly reduced and manufactured economically.

As described above, the present inventors have provided a method for producing 2-chlorobenzothiazole that is extremely economical and generates little industrial waste.

B) Examples The present invention will be specifically illustrated by Examples and Comparative Examples, but the invention is not limited thereto.

Example 1 (Synthesis of 2-chlorobenzothiazole) 2-chlorobenzothiazole was placed in a 300 ml four-hole flask equipped with a thermometer, a stirrer, a gas inlet tube, and a condenser connected to a gas absorption bottle.
Mercaptobenzothiazole 1 ((19' powdered sulfur 3
72' and introduced chlorine 4]2.

During this time, the reaction temperature rose to 96°C due to the heat of reaction. After the introduction of chlorine, further post-stirring completes the synthesis of Row V., 2-chlorobenzothiazole.

Next, in V1, an aqueous sodium carbonate solution is gradually poured into the reactant to effect neutralization. At that time, sulfur precipitates, so e
Separate separately. Next, Vh is attached to the sulfur separated by r.
To recover 2-chlorobenzothiazole, 100 ml of toluene! Wash the sulfur with water. The sulfur content at this time was 437'.

After filtration, the aqueous layer and the toluene layer obtained by extracting and dissolving 2-chlorobenzothiazole are separated, and the toluene is distilled and recovered. Chlorbenzothiazole 637 (yield 77
．． 6%).

The elemental analysis values were as follows.

Analysis value (%) C: 49.32 H: 2.2ON: 8
．． 20 S: 18.50 Calculated value (%) C: 49.56 H: 2.36 N: 8
．． 26 S: 1 s, 88 The analysis value by gas chromatography (FID) was 99.2% purity.

Example 2 (Synthesis of 2-chlorobenzothiazole) In the same manner as in Example 1, 2-mercaptobenzothiazole 802'
and the sulfur obtained in Example 1, and 4.852" of chlorine were introduced. An aqueous solution of caustic soda was used for neutralization, and ethylene dichloride H)om, ff was used as the extraction solvent.
use.

By distillation, the target product 2-chlorobenzo purity 99
．． It was 2%.

Example 3 (Synthesis of 2,5-dichlorobenzothiazole) 5-chloro-2-mercaptobenzothiazole is introduced.

The apparatus and the operation up to neutralization with an aqueous sodium carbonate solution were performed in the same manner as in Example 1. After neutralization, toluene]00mj'
[2.5-i) Extract all of the benzothiazole. The toluene was separated and recovered by distillation, and recrystallized with acetone.
C) Obtained.

The analysis value by gas chromatography (FID) showed that the purity was 98.1%.

Example 4 (Synthesis of 2,1-dichlorobenzothiazole) Recrystallization from 5-chloro-2-mercaptobenzothiazo-acetone in 2 rows V), the target product 2β-dichlorobenzothiazole was 5652 (yield 69%, melting point 69-71
°C) obtained. Gas chromatography (FII
)) analysis value is pure open 99. (It was 1%.

Comparative Example 2 - Sulfur monochloride 71y is added dropwise to mercaptobenzothiazole 807, followed by stirring to complete the reaction. After the reaction, 517 (yield: 63%) of the target product, 2-chlorobenzothiazole, is obtained by distillation.

The analysis value by gas chromatography (FID) was 980% purity.The amount of by-product b (of the distillation residual aroma) was much larger than that in the example.

(E) Effects of the Invention From Examples The present invention is a highly economical method for synthesizing and purifying 2-chlorobendithiabules in Fuchu.

Claims (2)

[Claims] (1) Formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼………………(I) [In the formula, R represents either a methyl group, a halogen group, or a hydrogen atom. The method is characterized in that a mixture of 2-mercaptobenzothiazoles represented by the following formula and solid sulfur is reacted with chlorine in the presence or absence of an organic solvent. Formula (II) ▲There are mathematical formulas, chemical formulas, tables, etc.▼………………(II) [In the formula, R represents either a methyl group, a halogen group, or a hydrogen atom. ] A method for producing 2-chlorobenzothiazoles. (2) Formula (III) ▲There are mathematical formulas, chemical formulas, tables, etc.▼………………(III
) [In the formula, R represents any one of a methyl group, a halogen group, and a hydrogen atom. ] Formula (IV) obtained by reacting chlorine with a mixture of 2-mercaptobenzothiazoles and solid sulfur ▲There are mathematical formulas, chemical formulas, tables, etc.▼……………………(IV) [Formula In the formula, R represents a methyl group, a halogen group, or a hydrogen atom. ], 2-chlorobenzothiazoles are combined with dilute alkali hydroxides, dilute alkali metal carbonates,
Alternatively, a method for producing 2-chlorobenzothiazoles, which comprises neutralizing and purifying using dilute alkali hydrogen carbonate.