CS266776B1 - Method for preparing 6-nitro-2-benzothiazolinone - Google Patents

Abstract

The subject of the solution is the method of preparation of 6-nitro-2-benzothiazolinone of formula I by oxidation of 6-nitro-2-benzothiazolinthione with potassium permanganate in the presence of alkaline hydroxide and subsequent decomposition of the resulting intermediate in an acidic environment. The compound can be used as a reactive intermediate for the synthesis of plant growth regulators, fungicides and other substances.

Description

The present invention relates to a process for the preparation of 6-nitro-2-benzothiazolinone of formula I (1).

The title compound was prepared by nitration of 2-benzothiazolinone (Fridman, S. G., W. Ch. 24, 642 (1954)) in 54% yield. Another known method of preparation is the hydrolysis of sulfones in an acidic (92% yield) or alkaline (91% yield) medium (I. Ya. Postovsky, I. A. Alexeyeva, Ž.

A hitherto undescribed process for the preparation of said compound has now been found, which is characterized in that 6-nitro-2-benzothiazolinethione is reacted with potassium permanganate in an alkaline medium.

The new process for the preparation of 6-nitro-2-benzothiazolinone found has the advantage over that described, starting from 6-nitro-2-benzothiazolinethione, which is readily available by nitration of the technical rubber accelerator known in the Czechoslovak Republic. While the preparation of 2-benzothiazolinone, from which 6-nitro-2-benzothiazolinone is produced by nitration, is time-consuming and energy-intensive in the decomposition phase of potassium 2-benzothiazol sulphonate, while the analogous potassium 6-nitro-2-benzothiazol sulphonate takes place almost immediately after acidification at room temperature, which saves time and energy.

The reaction can be carried out in a batchwise manner in a universal apparatus, it does not require the construction of a single-purpose apparatus.

The invention is useful for the preferred preparation of 6-nitro-2-benzothiazolinone, a reactive intermediate for the synthesis of fungicides (Idemitsu Kosan Co Ltd., Japan Pat. No. 60,105,604 (1985)), plant growth regulators (D'Amico JJ, U.S. Pat. 4,282,029 (1981) and others), as well as for other syntheses of compounds with putative biological activity.

The following examples illustrate, but do not limit, the process for preparing 6-nitro-2-benzothiazolinone from 6-nitro-2-benzothiazolinethione by oxidation followed by hydrolysis.

Example 1

Preparation of 6-nitro-2-benzothiazolinone, procedure A

6-Nitro-2-benzothiazolinolethione (25.4 g, 0.12 mol) was dissolved in a solution of potassium hydroxide (18 g, 0.32 mol) in water (300 cm 3). The mixture was heated to clear, then a solution of potassium permanganate (40 g, 0.25 mol) dissolved in water (800 cm ³ ) while hot was added in small portions. After all the permanganate had been added, the solution was heated to boiling, the magnesium oxide was filtered off with suction and washed with water until the colored washing water drained off. All liquid wells were pooled and decolorized with activated charcoal. The solution was acidified to pH 3 with sulfuric acid diluted 1: 1 with water and heated to reflux for 15 minutes. Immediately after acidification, crude 6-nitro-2-benzothiazolinone with a melting point of 247-252 ° C began to precipitate. The yield was 65.6 g (93.0%). The sample for analysis was purified by dissolving it in a 1: 1: 1 mixture of acetone-ethanol-water and precipitating with water after decolorizing with activated carbon.

Pure 6-nitro-2-benzothiazolinone with m.p. t. 250.5 to 252.5 ° C. The literature states t. t. 249-250 ° C (Postovskij I. Ya., Alexejeva, IA, Ž. Obč. Chim. 23, 1 905 (1953)), 248 ° C (Fridmen SG Ž. or 253 ° C (Eichi Ochiai Kazumasa Kokeguchi, Masao Shimizu, Hiroshi Nishizawa, J. Pharm. Soc. Japan, 63, 258 (1943)).

For C ₇ H ₄ N ₂ O ₃ S (196.19)

265776 calculated: C 42.86 H 2.06 N 14.28 S 16.34 found: 42.57 1.89 14.23 16.19

Example 2

Preparation of 6-nitro-2-benzothiazolinone, procedure B

Oxidation of 6-nitro-2-benzothiazolinethione was performed according to Example 1. After aspiration of the manganese dioxide, washing with water and decolorization with activated charcoal, hydroxylammonium chloride (35 g, 0.5 mol) was added to the filtrate, 6-nitro- 2-benzothiazolinone. The yield of crude product was quantitative. '. ·, \

A sample for analysis was purified according to Example 1. Pure 6-nitro-2-benzothiazolinone with m.p. t. 250 to. 253 ° C, which did not give depression t. t. with the product of Example-1.

For C ₇ H ₄ N ₂ O ₃ S (1-6.19) calculated%: C 42.86 H 2.06 N 14.28 S 16.34 found%: 42.67 1.85 14.06 16.54

The compound of the invention is used as a reactive intermediate for the synthesis of plant growth stimulators (D'Amico JJ, U.S. Pat. No. 4,282,029 (1981) and others) and fungicides (Idemitsu Kosan Co. Ltd. Jap. Pat. No. 60,105,604 (1985) ) and for other syntheses.

Claims (1)

OBJECT OF THE INVENTION A process for the preparation of 6-nitro-2-benzothiazolinone of formula I, N ° ₂ C ^{= 0} wherein, by oxidation of 6-nitro-2-benzotiazolíntión potassium permanganate in the presence of an alkali hydroxide and the resulting 6-nitro-2-benzotiazolsulfónan alkali quenched by acidifying its solution at 20 to 100 ° C without isolating the intermediate.