2- Aminoquinoxalines preparations

Numerous other methods are available for the preparation of amino derivatives, and these include direct synthesis (see Section 2.14.3.2) and more traditional transformations such as the Hofmann reaction. Aminopyrazine has been prepared from pyrazinamide (60G1807) and 2-aminoquinoxaline from the corresponding carboxamide (71JOC1158). The... 

Note For the preparation of nuclear or extranuclear secondary or tertiary aminoquinoxalines but rarely used recently. 

Naturally these reactions are applicable only to primary aminoquinoxalines. The diazonium salt is prepared in aqueous or nonaqueous solution and then converted into the required product as illustrated in the following classified examples. 

Various 3-substituted aminoquinoxaline-2-thiones have been prepared from quinoxaline-2,3-dithione. For example, treatment of the dithione with methylamine yields 3-methylaminoquinoxaline-2-thione, and the corresponding reaction with hydrazine hydrate yields 3-hydrazino-quinoxaline-2-thione. The latter compound is also obtained by treatment of 2,3-dichloroquinoxaline with thiourea and then with hydrazine hydrate. When 2-chloroquinoxaline 1-oxide is heated with thiourea in methanol at room temperature, an unidentified solid m.p. 184-185° is obtained alkaline hydrolysis of methanol-soluble products gives quinoxaline-2-thione in 41% yield. A method of some general applicability is illustrated by the preparation of the thioxo compound 4 from o-anilinoaniline (3). °... 

Bromoquinoxaline has been prepared by heating quinoxalin-2-one with phosphoryl bromide at 120°, and a series of 2-bromo-3-alkyl-quinoxalines have been prepared in analogous fashion. 2-lodoquinoxaline is prepared by the action of sodium iodide and hydriodic acid on 2-chloroquinoxaline and 2-fluoroquinoxaline by application of the Balz-Schiemann reaction to 2-aminoquinoxaline. ... 

The most common substrates for the preparation of aminoquinoxalines are the corresponding chloro compounds. 2-Aminoquinoxaline itself has... 

Quinoxaline-2-carboxamides have been used in the preparation of 2-aminoquinoxalines these derivatives are converted into the corresponding amines by treatment with sodium hypohalite under normal Hofmann-type conditions. 2-Aminoquinoxalines have been prepared by the reduction of aminoquinoxaline N-oxides with hydrogen and a Raney Ni catalyst, and 2-anilinoquinoxaline has been obtained from hydrolysis of... 

Condensation of o-phenylenediamine with the p-dimethylaminoanils of aroylcyanides in hot glacial acetic acid yields 2-amino-3-aryl(heteroaryl)quinoxalines (Scheme 3). The required anils may be prepared in situ from the appropriate benzylpyridinium bromide (ArCH2l C5H5Br ), p-nitrosodimethylaniline, and sodium cyanide. A related method of aminoquinoxaline synthesis involves the condensation of o-nitrosoaminobenzenes with a benzyl cyanide and gives products of unambiguous structure (Scheme 4). ... 

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