CS255243B1 - 6-Bromo-6- (4-pentyloxyphenyl) -3 (2H) -pyridazinone and its method of preparation - Google Patents

Abstract

The invention relates to 5-bromo-6-(4-pentyloxyphenyl)-3(2H)-pyridazinone of formula I and a method of preparation which consists in the reaction of 3-bromo-4-oxo-4-(4-pentyloxyphenyl)-2-butenoic acid methyl ester with hydrazine or hydrazine hydrate. This substance serves as an intermediate for the preparation of anthelmintics.

Description

The invention relates to 5-bromo-6- (4-pentyloxyphenyl) -3 (2H) -pyridazinone of formula I

Br

^OC 5 ^H I (I) and its preparation process.

This new undescribed substance serves as an intermediate for the preparation of substituted 5-amino-6- (4-pentyloxyphenyl) -3 (2H) -pyridazinones with anthelmintic effect of MS. AO No 255 242.

The compound of the formula I can be prepared by the reaction according to the invention, characterized in that the known 3-bromo-4-oxo-4- (4-pentyloxyphenyl) -2-butenoic acid methyl ester (Zikán V., Semonský M., Skvorová) H., Kakac B., Holubek J., Vesela H .: Collection Czechoslovak Chem. Commun. 41, 3 113 (1976)) reacts with hydrazine or hydrazine hydrate or an aqueous solution of hydrazine hydrate in an inert organic solvent, preferably an alkanol having from 1 to 4 carbon atoms, at -10 to 40 ° C, preferably at -5 to 20 ° C.

The compound of the invention was prepared by reacting 3-bromo-4-oxo-4- (4-pentyloxyphenyl) -2-butanoic acid methyl ester with hydrazine hydrate or hydrazine or an aqueous solution of hydrazine hydrate at -5 to 5 ° C in ethanol, whereupon the temperature of the reaction mixture was allowed to rise to 20 ° C. Using hydrazine or hydrazine hydrate, over 90% of the theory of a compound of formula I of satisfactory purity was obtained; when using an aqueous solution of hydrazine hydrate, the yield was lower.

The following examples illustrate the invention but do not limit it.

Example 1

To a solution of 6.4 g (186 mmol) of 93% hydrazine in 80 mL of ethanol was added dropwise a solution of 35.5 g (100 mmol) of methyl 3-bromo-4-oxo-4- (4-pentyloxyphenyl) -2- butene in 80 ml of ethanol at 1 to 5 ° C and the suspension is stirred for 1 h at room temperature. A total of 32.28 g (96%) of product is obtained by suctioning off the reaction mixture and treating the mother liquors after suction. 198 DEG-199 DEG C. and composition

Example 2

To a solution of 42 g (0.839 mol) of 100% hydrazine hydrate in 500 ml of ethanol is added with stirring a solution of 231 g (0.650 mol) of methyl 3-bromo-4-oxo-4- (4-pentyloxyphenyl) -2-butenoate in 500 ml. ethanol so that the temperature of the reaction mixture is between -10 and -6 ° C. The mixture was further stirred for 1 h at -6 to -3 ° C and then for 1 h at room temperature. The work-up described in Example 1 afforded 199.1 g (91%) of product which melts at 198.2-199.4 ° C after crystallization from ethanol.

Example 3

To a solution of 12 g (0.192 mol) of 80% aqueous hydrazine hydrate in 100 ml of ethanol is added dropwise a solution of 53.25 g (0.15 mol) of 3-bromo-4-oxo-4- (4-pentyloxyphenyl) -2-butenoic acid methyl ester. in 120 ml of ethanol at a temperature of -2 to 0 ° C. The suspension was stirred at 0 ° C for 1 h and then at room temperature for 1 h. Working up according to Example 1 gives 38 g (75%) of a product which melts at 198.3-199 ° C after crystallization from ethanol.

Claims (3)

OBJECT OF THE INVENTION 1. 5-Bromo-6- (4-pentyloxyphenyl) -3 (2H) -pyridazinone of Formula I OC _E ^H 11 2. A process for the preparation of a compound according to claim 1, wherein the 3-bromo-4-oxo-4- (4-pentyloxyphenyl) -2-butenoic acid methyl ester is treated with hydrazine or hydrazine hydrate or an aqueous solution of hydrazine hydrate in a medium % of an inert organic solvent at -10 to 40 ° C. 3. Process according to claim 2, characterized in that the organic solvent is a C1-C4 alkanol, in particular ethanol, at a temperature of -5 to 20 [deg.] C.