DE1620180C3 - Process for the preparation of quinoxaline di-N-oxides - Google Patents

Description

example 1

1-morpholino-cyclohexene became a warm one given methanolic solution of isobenzofuroxane, which formed a deep red color and the The temperature of the reaction mixture rose. The concentration of the reaction mixture was 43% Yield of l, 2,3,4-tetrahydrophenazine-N, N'-di-oxide of the formula IV as a pale red solid body with the Melting point 183 to 185 ° C with decomposition. Recrystallization from methanol gave yellow prisms, which in 185 ° C melted with decomposition.

65

(IV)

Example 2

The same product was obtained when, in Example 1, l-pyrrolidino-cyclohexene was used instead of 1-morpholinocyclohexene was used.

Example 3

Following the general procedure of Example 1, using 1-morpholino-cyclopentene 2,3-trimethylene-quinoxaline-N, N'-dioxide of the formula V, which melts at 182 ° C. with decomposition obtain.

(V)

lino-ethylene obtained the 2-phenylquinoxaline-N, N'-dioxide of the formula VI which ^{melts at 21O 0 C.}

(VI)

Example 5

Using the general procedure described in Example 1, 2-morpholinochole esters were made the 2,3-cholestano [b] quinoxaline-N, N'-dioxide of the formula VII which melts at 208 ° C. is obtained.

CrHi-

(VII)

m example 4

Using the general procedure given in Example 1, 1-phenyl-1-morpho-

Claims (1)

Claim: Process for the preparation of quinoxaline di-N-oxides of the general formula I. (D wherein R is a hydrogen atom or for one or more halogen atoms, nitro, alkyl or alkoxy groups and alkyl and alkoxy groups can be closed to form a ring and in which A a phenyl radical and B a hydrogen atom, an alkyl, alkoxy, alkoxyalkyl, phenyl or phenylalkyl radical or A and B together represent the trimethylene or tetramethylene radical or with the the two carbon atoms to which they are bound form the 2,3-cholestano radical, characterized in that that an isobenzofuroxan of the formula II Amino residue 10 15th 20th 25th (Π) in which R has the meaning given, in an inert solvent at elevated temperature with an enamine of the general formula III 30th 35 (III) in which A and B have the meaning given above. Quinoxaline di-N-oxides are used to control several pathogenic microorganisms as well as intermediate products in the manufacture of other closely related ones Compounds useful which have similar antipathogenic activity. In German patent 8 64 554 and in US patents 28 91 062 and 29 21 937 is the Production of quinoxaline di-N-oxides described by processes in which a direct oxidation of Quinoxaline compounds takes place. According to this method, for the preparation of a particular di-N-oxide, the corresponding quinoxaline compound required as a starting material, which z. B. from an o-phenylenediamine and 1,2-diketones. That being said, oxidation reactions are to some extent not selective and are notable in usually through low yields of the desired product and formation of one or more difficult to separate by-products. 50 55 60 The invention was based on the object of producing quinoxaline di-N-oxides by a process which avoids the direct oxidation of a quinoxaline compound. The subject of the invention is the method characterized in the claim. The process according to the invention for the preparation of quinoxaline di-N-oxides is distinguished among others characterized in that the desired compounds are relatively free from by-products that are difficult to separate are. Albeit as enamines, the alkylamines such as the lower dialkylamines and especially secondary cyclic amines Amines such as pyrrolidine and morpholine are preferred, the invention does not apply to specific amine moieties Exit amines limited. The reaction between isobenzofuroxane and the enamine reaction component is carried out by adding the Enamine to a warm solution of isobenzofuroxane in a solvent such as methanol, ethanol or Dioxane. The solid product is conveniently isolated by evaporation of the solvent. It can be further purified by recrystallization from solvents. Chemical and physical properties confirm the di-N-oxide structure of the process products. For example, the infrared spectrum of the 1,2,3,4-tetrahydrophenazine-N, N'-dioxide obtained according to the method according to the invention shows strong bands at 1320 and 1300 cm- ¹ , which can be assigned to the N-oxide structure. The reduction of this compound with sodium dithionite gave 1,2,3,4-tetrahydrophenazine, which in turn could be oxidized back to Ν, Ν'-dioxide. Reduction with sodium borohydride gave cis-1,2,3,4,4a, 5,10,1 Oa-octahydrophenazine. The isobenzofuroxan itself required as a starting material, which is also known as benzofuroxan or benzofurazan-N-oxide is called, according to Organic Synthesis, 37 (1957), pp. 1 to 2, easily through Treating o-nitroaniline with sodium hypochlorite available. The enamines are extremely convenient by reacting the corresponding ketones with a secondary amine produced. The invention is further illustrated by the following examples: