Preparation of ammonium salts of 3-isopropyl-2, 1, 3-benzothia-d

Details Preparation of ammonium salts of 3-isopropyl-2, 1, 3-benzothia-d Preparation of ammonium salts of 3-isopropyl-2, 1, 3-benzothia-d

1997-08-15

1998-08-18

Ford, John M.

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

Organic compounds

Heterocyclic carbon compounds containing a hetero ring...

C07D28516

Patent

active

057959838

DESCRIPTION:

BRIEF SUMMARY
This is a 371 of PCT/EP96/00420, filed Feb. 1, 1996.


BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to processes for preparing salts of 3-isopropyl-2,1,3-benzothiadiazin-4-one 2,2-dioxide of the general formula I ##STR2## where the radicals R.sup.1, R.sup.2, R.sup.3 and R.sup.4 independently of one another are hydrogen, lower alkyl or lower hydroxyalkyl.
2. Description of the Background
Herbicidal benzothiadiazin-4-one 2,2-dioxides are disclosed in DE-A 15 42 836, DE-A 21 64 459 and DE-A 22 17 722. Ammonium salts are also mentioned therein as an application form, the ammonium, methylammonium, trimethylammonium, ethylammonium, diethanolammonium and ethanolammonium salts being particularly mentioned.
It is furthermore generally known that the sodium salt, the calcium salt and the potassium salt of 3-isopropyl-2,1,3-benzo-thiadiazin-4-one 2,2-dioxide (INN name: bentazone) are very hygroscopic. In the case of solid formulations of these salts, this leads to the product forming lumps as a result of atmospheric humidity or even deliquescing and thereby no longer being meterable without problems.
If these salts are introducecd into water-soluble film bags, the latter are furthermore dehydrated by interaction of the hygroscopic active compounds with the films. This results in the films becoming brittle, ie. their storage stability is no longer guaranteed.
In the synthesis of bentazone, the active compound is customarily obtained in neutral form and as a rule dissolved in an organic solvent (cf. DE-A 27 10 382).
Usually, the active compound is then converted into one of its salts, as these improve the bioavailability of bentazone.
U.S. Pat. No. 5 266 553 discloses, for example, the formulation of ammonium salts of bentazone as flowable water-soluble solids. For this purpose, according to the general description in the patent an aqueous mixture of the ammonium salt is first prepared. The solid formulation of the active compound is obtained from this by evaporating all of the solvent and subjecting the product to aftertreatment with a neutralizing base. The evaporation step with concomitant use of water as a solvent, however, necessitates a high expenditure of energy and the active compound is exposed during the course of this to the increased evaporation temperature for a very long time.


SUMMARY OF THE INVENTION

It is an object of the present invention to provide processes for preparing ammonium salts of bentazone in which the disadvantages of the preparation process described above are avoided completely or in part.
We have found that this object is achieved by a process for preparing salts of 3-isopropyl-2,1,3-benzothiadiazin-4-one 2,2-dioxide of the general formula I ##STR3## where the radicals R.sup.1, R.sup.2 and R.sup.3 independently of one another are hydrogen, lower alkyl or lower hydroxyalkyl, which comprises reacting 3-isopropyl-2,1,3-benzothiadiazin-4-one 2,2-dioxide (IIa) ##STR4## in an organic solvent with an amine of the general formula IIIa ##STR5##
We have additionally found a process for preparing salts of 3-isopropyl-2,1,3-benzothiadiazin-4-one 2,2-dioxide of the general formula I ##STR6## where the radicals R.sup.1, R.sup.2, R.sup.3 and R.sup.4 independently of one another are hydrogen, lower alkyl or lower hydroxyalkyl, which comprises ##STR7## in a virtually water-immiscible organic solvent and, if desired, in the presence of water, with an amine of the general formula IIIa ##STR8## or an ammonium salt of the general formula IIIb ##STR9## where X is the anion of an acid of pK.sub.A greater than 4 or the hydroxyl ion and n is equal to the number of negative charges on the anion X, and
Moreover, we have found a process for preparing salts of 3-isopropyl-2,1,3-benzothiadiazin-4-one 2,2-dioxide of the general formula I ##STR10## where the radicals R.sup.1, R.sup.2, R.sup.3 and R.sup.4 independently of one another are hydrogen, lower alkyl or lower hydroxyalkyl, which comprises ##STR11## in water with an ammonium salt of the general formula IIIb ##STR12## wh

REFERENCES:
patent: 3012870 (1961-12-01), Rechter
patent: 5266553 (1993-11-01), Champion et al.
Kirk-Othmer: "Encyclopedia of Chemical Technology. 4.sup.th ed., vol. 2" 1992, John Wiley & Sons, New York XP002007803.

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