JPS597179A - Improved preparation of 2-hydrazinobenzothiazoles - Google Patents

Abstract

PURPOSE:To obtain the titled substance useful as a raw material for agricultural chemicals, drugs, etc. by reacting a 2-aminobenzothiazole with hydrazine, to improve its purity industrially inexpensively without causing coloring, by using a specific solvent containing an alcoholic hydroxyl group. CONSTITUTION:A 2-aminobenzothiazole shown by the formula (R is H, halogen, lower alkyl, or lower alkoxy) is reacted with hydrazine in a solvent selected from 4-8C alkyl alcohol, cyclohexanol, benzyl alcohol, furfuryl alcohol, tetrahydrofurfuryl alcohol and hexylene glycol in the presence of an acid at 95-125 deg.C, to give the titled compound. Since the 2-aminobenzothiazole is obtainable easily in the form of hydrochloric acid, hydrobromic acid, etc., the same mineral acid is preferably used as the acid. An organic acid such as acetic acid, oxalic acid, etc. may be used.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing 2-hydrazinobenzothiazoles, which are chemical compounds. More specifically, the present invention relates to an improved method for producing 2-hydrazinobenzothiazoles by reacting 2-a[epsilon]nobenzothiazole and hydrazine in a specific alcohol solvent.

Until now, a method for producing 2-hydrazinobenzothiazoles by reacting 2-aminobenzothiazoles and hydrazine in a solvent such as C2-C4 1-lugylene diol in the presence of an acid has been proposed in Japanese Patent Application Laid-open No. It is reported in the publication No. 49-80065. However, the 2-hydrazinobenzothiazoles produced by this method have low purity and are extremely colored, resulting in unsatisfactory products.

The inventors of the present invention have conducted intensive studies on a method for industrially providing high-purity 2-hydrazinobenzothiazoles at low cost, and found that when a specific solvent having an alcoholic hydroxyl group is used, it reacts specifically and causes coloration. High purity 2-
It was discovered that hydrazinobenzothiazoles can be obtained, and the present invention was completed.

That is, 1 the present invention provides a method for reacting 2-aminobenzothiazoles represented by the general formula (wherein R represents a hydrogen atom, a halogen atom, a lower alkyl or a lower alkoxy group) with hydrazine in the presence of an acid, In the method for producing 2-hydrazinobenzothiazoles, a furkyl alcohol having 4 to 8 carbon atoms (7),
This is an improved method for producing 2-hydrazinobenzothiazoles, characterized in that the reaction is carried out in a solvent selected from cyclohexyl alcohol, benzyl alcohol, furfuryl alcohol, tetrahydrofurfuryl alcohol, and hexylene glycol.

The 2-aminobenzothiazoles conveniently used in the present invention can be produced by known synthesis methods. Moreover, many of them are easily available industrially. For example, 2-aminobenzothiazole, 2-amino-4-methylbenzothiazole, 2-
Amino-6-methylbenzothiazole, 2-amino-4
-ethylbenzothiazole, 2-amino-4-chlorobenzothiazole, 2-amino-6-chlorobenzothiazole, 2-amino-4-methoxybenzothiazole, 2
-amino-6-methoxybenzothiazole, 2-1mino-6-nitoxybenzothiazole, and the like.

In the method of the present invention, corresponding 2-hydrazinobenzothiazoles can be produced from these 2-aminobenzothiazoles.

The hydrazine used in the present invention may contain water, and various easily available industrial products can be used.

The amount used is 1. Normally, in the conventionally known methods, 1 part is used in large excess as a solvent, but this is not economically preferable, and it is desirable that the amount be as close to the theoretical amount as possible.

In the present invention, 1 to 1 mole of 2-1 minobenzothiazole
It is 5 times the molar amount, preferably 2 to 4 times the molar amount. It made it possible to drastically reduce weight.

The acid used in the present invention may be used alone in the reaction, but it can also be used in the form of a 2-aminobenzothiazole salt or a hydrazine salt.

It is most preferred to use the same mineral acids since 2-aminobenzothiazoles are readily available in the form of hydrochloric, hydrobromic or sulfate salts. However, organic acids such as acetic acid, benzoic acid, formic acid, oxalic acid or p-toluenesulfonic acid can also be used.

The amount of acid used is 0.1 per mole of hydrazine.
The reaction proceeds when used in a ratio of 0.25 to 1 mol, preferably 0.25 to 5 mol.

Among the solvents used in the present invention, alkyl alcohols having 4 to 8 carbon atoms [are n-butanol, inbutanol%
Examples include 5eC-butanol, 1ao-amyl alcohol, methylamyl alcohol, 2-ethyl-1-butanol, and n-octatool.

Furthermore, a solvent selected from cyclohexanol, benzyl alcohol, furfuryl alcohol, tetrahydrofurfuryl alcohol, and yohyhexylene glycol is used.

The reaction temperature is selected depending on the type of 2-1 minobenzothiazole, solvent, reaction time, etc.

The reaction is usually carried out at a temperature of 90°C or higher, preferably 95 to 125°C.

In the post-treatment of the present invention, 2-hydrazinobenzothiazoles have low solubility at room temperature or lower in the solvent used in the present invention. However, since the raw material 2-aminobenzothiazole has a relatively high solubility, even if it remains unreacted, only the target product can be precipitated by cooling the reaction solution, and it can be easily separated out without filtration. .

The 2-hydrazinobenzothiazoles produced by the method of the present invention are highly pure and have almost no 1 coloration. However, if necessary, it can be purified by recrystallization using the solvent used in the present invention.

In the above-mentioned Japanese Patent Application Laid-open No. 49-80065, C1~
Although the 2-hydrazinobenzothiazoles were purified by recrystallization using alcohol No. 3, when the present inventors conducted a supplementary test, the purity of the 2-hydrazinobenzothiazoles decreased, and the crystals were significantly colored.

When the solvent of the present invention is used, such a phenomenon does not occur, and not only can the purity be increased, but also colored substances can be removed.

The present invention will be explained in detail below with reference to Examples.

Example 1 49,5 of 2-amino-4-methylbenzothiazole
P CO0.5 mol) and 80% hydrazine hydrate 56.5 P
C0.9%k) and ik hexylene glycol 500dl
C dispersed and acetic acid 27. OF (0.45 mol) was added at room temperature. This mixture was then diluted with VCl2 under a nitrogen atmosphere.
The mixture was heated and stirred at 0°C for 4 hours. Cool to room temperature, filter the precipitated crystals, wash with a little silane glycol and dry to obtain 47.5 r of 2-hydrazino-4-methylbenzothiazole (88% of theory) as white needle-like crystals. I got it.

Melting point: 168-170℃, purity determined by iodometric titration: 98%
Met.

Recrystallization from silane glycol yielded 39.
IP, melting point 171-172°C, purity 99.5% @ Comparative Examples 1-5 The reaction was carried out in the same manner as in Example 1 except that the solvent was changed, and 2-hydrazino-4-methylbenzothiazole was obtained. Ta. The results are shown in the table below.

Example 2 2-amino-4-chloroΩbenzothiazole 55.4t (
0,3-E-nyl) and 80% hydrazine hydrate 57.5 r
([16 moles) and arsenic sulfate)")") 59. Ot
((L5' mol) was dispersed in 300% of furfuryl alcohol and heated and stirred at 110 cV under a nitrogen atmosphere for 3 hours. Treated in the same manner as in Example 1 to obtain 4-chloro-2-hydra in the form of white needle-like crystals. Dinobenzothiazole 55. I P
(92% of theory) was obtained. The melting point was 227-229°C, and the purity was 98%.

Examples 3 to 9 The reaction was carried out in the same manner as in Example 2 except that the solvents shown in the following table were used to obtain 4-chloro-2-hydrazinobenzothiazole. The results are shown in the table below.

Example 10 Hydrobromide of 2-avano-4-methylbenzothiazole 7.55 F (α06 mol) was dispersed in hexylene glycol 50- and 80% hydrazine hydrate 7,51 P
(α12 mol) was added dropwise at room temperature. Then, the mixture was heated and stirred at 120° C. for 4 hours under a nitrogen atmosphere. Thereafter, the same procedure as in Example 1 was carried out to obtain 5.05 r (94% of the theoretical amount) of 2-hydrazino-4-methylbenzothiazole in the form of white needle-like crystals.

The melting point was 167-170°C, and the purity was 98%.

Examples 11 to 14 Reactions were carried out in the same manner as in Example 10, except that the type of 2-aminobenzothiazole was changed. The results are shown in the table below. however,
R- in the table is

Claims (1)

[Claims] A 2-aminobenzothiazole represented by the general formula (wherein R is a hydrogen atom, a rhodane atom, a lower alkyl or a lower alkoxy group) is reacted with hydrazine in the presence of an acid. , in a method for producing 2-hydrazinobenzothiazoles, reacting in a solvent selected from alkyl alcohols having 4 to 8 carbon atoms, cyclohexanol, benzyl alcohol, furfuryl alcohol, tetrahydrofurfuryl alcohol, and hexylene glycol. An improved method for producing 2-hydrazinobenzothia l-ols, characterized by: