Process for preparing 4-isothiazolin-3-one

Details Process for preparing 4-isothiazolin-3-one Process for preparing 4-isothiazolin-3-one

1994-02-04

1995-09-26

Gerstl, Robert

Organic compounds -- part of the class 532-570 series

Organic compounds

Heterocyclic carbon compounds containing a hetero ring...

C07D27503

Patent

active

054535077

DESCRIPTION:

BRIEF SUMMARY
This Application is a 371 of PCT/KR 92/00014 filed May 11, 1992.


BACKGROUND OF THE INVENTION



Field of the Invention

The present invention relates to a process for preparing 4-isothiazolin-3-one, in particular to improved method for selectively preparing 4-isothiazolin-3-one having the following structural formula(I) which is useful as an antiseptic or anti-infectives in the field of cooling waters or metal processing oils for industrial, paints, cosmetics, sufactants, sensitizers. etc. ##STR2## wherein. R.sup.1 is methyl or n-octyl group:
European Patent Publication No. 0095907 discloses a method for manufacturing 4-isothiazolin-3-one derivatives as a mixture of two substance by carring out amidation reaction in accordance with the following scheme(A) and cyclization reaction of the following scheme(B). ##STR3##
Also, Journal of Heterocyclic Chemistry, 1971, 8 discloses a synthetic method of 2-t-octyl-4-isothiazolin-3-one having structure being similar to the above formula(I), by carting out amidation reaction in accordance with the following scheme(C) and chlorization and cyclization according to the following scheme(D). ##STR4##
But, according to the method of European Patent Publication No. 0095907, mixture of two substance, 2-methyl-4-isothiazolin-3-one of the above formula(a) and 5-chloro-2-methyl-4-isothiazolin-3-one of the above formula(b), is manufactured as a necessary, and then 5-chloro-2-methyl-4-isothisolin-3-one of the formula(b) has higher virulence than the formula(a).
Therefore, the product mixed cannot be used for the human body, and cannot be used for a long time because of being stability at room temperature and so used within the limits. Also, the yield is low.
Nevertheless, a method for selectively preparing or separating the formula(a) has not been developed, and if it may be separated, the process is intricate and uneconomical. So, the mixed product has been used as it is.
The method disclosed in Journal of Heterocyclic Chemistry is to prepare 2-t-octyl-4-isothiazolin-3-one by using Cl.sub.2 gas and toluene as solvent on the scheme(D), but the product is not the compound of structure having n-octyl group.


SUMMARY OF THE INVENTION

The object of the present invention is to provide a new process for selectively preparing the compound of the above formula(I) to high yield.
The present invention relates to a process for selectively preparing 4-isothiazolin-3-one having the above sturctural formula(I) characterized in which consists of preparing 3,3'-dithiodipropionyldichloride of following formula(II), by reacting 3,3'-dithiodipropionic acid with thionylchloride, reacting with amine compound to prepare 3,3'-dithiodipropionamide derivative of following formula(III) and herein adding sulfurylchloride of following formula(IV) in organic solvent to cyclize. ##STR5## wherein, R.sup.1 is as defined in the above formula(I)


DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to the process for selectively preparing 4-isothiazolin-3-one of the above formula(I) by using 3,3'-dithiodipropionic acid, thionylchloride, amine compound and sulfurylchloride of the above formula(IV), and then 3,3'-dithiodipropionic acid is reacted with thionyl chloride to ratio of 1:2 to 1:4 by mole at 10.degree..about.30.degree. C. to obtain 3,3'-dithiodipropionyl dichloride of the above formula(II). If the reacting mole ratio of thionylchloride is less than 1:2, the unreacted impurity may be occured, and if excess of 1:4, it is uneconomical as unnecessary on the chemical reaction.
Also, if the reacting temperature is lower than 10.degree. C., the reation time is very long, and if over 30.degree. C., it is dangerous to operate because of generation of toxic thionylchloride vapor.
The compound of formula(II) is reacted with amine compound selected from methyl amine or n-octylamine to 1:2 to 1:6 by mole at -10.degree. C..about.35.degree. C., preferably -10.degree. C..about.30.degree. C., more preferably 15.degree. C. to room temperature.
If the reacting temperature is lower than -10.degree. C., i

REFERENCES:
patent: 5312827 (1994-05-01), Bayer
Lewis, J. Het. Chem 8, 571 (1971).
Miller et al., "Isothiazoles II: 5-Chloro-4-isothiazolin-3-ones," Research Division, Rohm and Haas Company, Spring House, Pa. Aug. 1971, vol. 8, pp. 581-586.

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