Selenazole-pyrazolones

By further reaction of the selenazole-pyrazolones with p-nitro-sodialkylanilines a number of pyrazolone-azomethines (18) was pre-... 

Hydrazono-5-(p-dialkylaminophenylimino)selenazoles, pyrazolone azomethin selenazoles, quinoid dyes, and formazans are other important dyes used in photography and the color industry (cf. previous sections). 

Despite the inconveniences, a certain number of studies have been carried out, particularly concerning dyes containing azomethine groups. Such as hydrazones, pyrazolones, formazans, and selenazoles quinoids. Saturated heterocycles, that is, selenazolines and selenazolidines. have also been tackled. Selenium derivatives for pharmacological or physiological applications are little developed by comparison with their thiazole homologs. 

As a further typical reaction of the hydrazine group of the 2-hydrazinoselenazoles (cf. Section I,C,2), pyrazolone formation was investigated. By condensation of the hydrazines with -ketoesters in acetic acid, it was possible to synthesize a series of l-(selenazol-2-yl)-3-alkylpyrazol-5-ones (16). ... 

The preparation of the selenazolyl-pyrazolones was then effected by a second method, in which first the pyrazolone ring and afterward the selenazole ring was formed. For this purpose -ketoester seleno-semicarbazones were first converted to the corresponding 1-seleno-carbamoyl-3-aIkylpyrazol-5-one. These, by condensation with a-halo-genocarbonyl compounds according to the Hantzsch synthesis, formed the selenazole ring as a second step (17). 

Pyrazolone azomethin selenazoles, dyes, photography and color industry,... 

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