DE1670169A1 - Process for the preparation of 4-amino-5-bromopyridazonen- (6) - Google Patents

Description

Process for the preparation of 4-amino-5-brompgrid.azonen- (6) It is known from the reports of Deutsche Chemischen Gesellechaft, Volume 32, 1899, page 534, that 4,5-dibromopyridazones can be obtained by reacting mucobromic acid with hydrazine receives. However, mucobromic acid is a compound that is not readily available. A variety of methods for halogen exchange in organic compounds are also known. In Houben-Weyl, Methods of Organic Chemistry, Volume 5/4, 1960, page 354, it is described that allyl chloride or benzyl chloride can be converted into the corresponding bromides with sodium bromide in aqueous solution at temperatures between 70 and 120 ° C . However, this method is only limited to compounds in which the chlorine atoms are activated. Another method of producing the bromine compounds from chlorine compounds is according to loc. ei,., page 355, the reaction of chlorine compounds with aluminum bromide. The process has the disadvantage that it must be carried out absolutely free of water, which means a lot of effort. Next is to loco eitot page 356, known that the transhalogenation can be carried out with hydrogen bromide. However, this procedure cannot be used with acid-sensitive compounds. In addition, the hydrogen bromide often contains small amounts of bromine, so that secondary reactions occur as a result of uncontrolled bromination. can. It has now been found that 4-.mino-5-bromopyridazone® (6) is obtained if 4-aemino-5-chloropyridazone- (6) with alkali.- or alkaline earth bromides, optionally in the presence of a flux, to temperatures between Heated between 150 and 400 ° C. The new process has the advantage that bromine-substituted pyridazones that were previously difficult to access can be obtained in a simple manner. This is remarkable in that there was a prejudice to replace non-activated chlorine atoms, such as those in chlorine-substituted pyridazones, with bromine, since according to Houben-Weyl, Met 'ioden der Organic Chemie, Volume 5/4, 1960, page 354, only. Compounds such as allyl or benzyl chloride are accessible to this reaction, borrowed. It was also surprising that the pyridazones allow the reaction at such high temperatures without significant decomposition. Preferred chlorine-substituted pyridazones have the formula. where R1 is a hydrogen atom or an aliphatic, cycloaliphatic, araliphatic or aromatic radical each having up to 12 carbon atoms. The radicals can have substituents such as carboxyl or amino groups or alkyl radicals with 1 to 4 carbon atoms bonded via 1.therbrückeno R2 denotes a hydrogen, chlorine or bromine atom, a hydroxyl or alkoxy group with 1 to 4 carbon atoms or an aromatic radical with 6 to 10 carbon atoms The radicals can optionally have substituents such as halogen atoms, carboxyl or amino groups or alkyl radicals with 1 to 4 carbon atoms bonded via ether bridges. R, means the rest where R5 and R6 can represent hydrogen atoms or alkyl, cycloalkyl, aralkyl or aryl radicals each having up to 12 carbon atoms and R5 and R6 together with the nitrogen atom they are substituting, optionally together with a sulfur or oxygen atom or the groups% NTi ,> SO or: .S02 denote common members of a 5- to 7-membered heterocyclic ring. The pyridazones accessible to the reaction are, for example, 1-phenyl-4-amino-5-chloropyridazon- (6), 4-morpholino-5-chlorpyriadzon- (6), 1-phenyl-4-phenylamino-5-chloropyridazon- (6), 1-methyl-4-amino-5-chloropyridazon- (6), 1-cyclohexyl-4-amino-5-chloropyridazon- (6), 1-cyclooctyl-4-amino-5-chloropyridazon- (6), 1- Isopropyl-4-amino-5-chloropyridazone- (6). Bromides suitable for the reaction are, for example, sodium bromide, galium bromide, magnesium bromide or calcium bromide. Expediently, 1 to 10 equivalents, preferably 1.1 to 2 equivalents, of the metal bromides are used for one equivalent of the chlorine to be replaced. The process is carried out in a melt. Either the starting pyridazones are melted together with a substance which has melted itself at the reaction temperature, e.g. urea or an alkali metal formate, or the substance is worked at temperatures above the melting point of the pyridazone to be converted. The reaction takes place at temperatures between 150 and 400 ° C. Particularly good results are obtained between 190 and 360 ° C. The process according to the invention is carried out, for example, by heating the pyridazones alone or together with a flux with the corresponding metal bromide in the ratio described to the temperatures indicated. The reaction can be carried out under normal pressure, but also under reduced or elevated pressure. The reaction is generally over after 1 to 10 hours. The bromopyridazones obtained or their mixtures with the starting pyridazones can then be used directly for further reactions or they can be applied directly as herbicides. They are also valuable intermediates in the manufacture of pharmaceuticals and dyes. The parts mentioned in the following example are parts by weight. Example 100 parts of 1-phenyl-4-amino-5-chloropyridazon- (6) are stirred with 100 parts of sodium bromide for 1 hour at 250 ° C. in a nitrogen atmosphere. The cooled, solidified: after crushing, the melt is digested with around 1000 parts of water. The insoluble parts are 105 parts. Pp. 205-208 ° C. The UR analysis showed a content of 41% unchanged 1-phenyl-4-amino-5-chloropyridazon- (6) and 5-7% 1-phenyl-4-amino-5-bromopyridazon- (6). The halogen determination showed 5.7% chlorine and 18.7% bromine. This corresponds to 36% of the chloropyridazone and 62% of the bromopyridazone. The yield of 1-phenylv4-amino-5-bromopyridazone- (6) can still be increased significantly if the pyridazone mixture thus obtained is reacted again.

Claims (1)

Patent claim A method for the preparation of 4-amino-5-brompyridazonen- (5), characterized in that 4-amino-5-ehlorpyridazone - (6) with alkali or Erdalkalibromiden, optionally in the presence of a flux, to temperatures between 150 and 40000 heated.