Action of Cu(II) salts on osazones: side reactions of osotriazole formation
✍ Scribed by Hassan El Khadem; Pawel Czubarow; Christian Sandstedt
- Publisher
- Elsevier Science
- Year
- 1992
- Tongue
- English
- Weight
- 245 KB
- Volume
- 224
- Category
- Article
- ISSN
- 0008-6215
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✦ Synopsis
It is known'" that sugar phenylosazones undergo cyclization in aqueous CuSO, to give phenylosotriazoles in yields ranging from 45-70%. In order to identify the side reactions responsible for the low yields, Cu(I1) salts were treated with two bis(phenylhydrazones) and two mono(phenylhydrazones) and the products analyzed by g.l.c.m-s. and h.p.1.c. The substrates used were D-arabino-hexulose phenylosazone, benzil bis(phenylhydrazone), D-mannose phenylhydrazone, and benzaldehyde phenylhydrazone. It was found that all four coumpounds underwent hydrolysis4 to give the parent carbonyl compound and phenylhydrazine.
During the reaction, phenylhydrazine was oxidized to benzene, nitrogen, and water by the Cu(I1) salt, which explains why reduced Cu and Cu,O are precipitated during osotriazole formatior?. The mono(phenylhydrazones) studied afforded hydrolysis products, whereas the bis@henylhydrazones) yielded cyclization and hydrolysis products. Thus, D-mannose phenylhydrazone yielded mannose and benzene, whereas benzaldehyde phenylhydrazone yielded benzaldehyde and benzene, all in quantitative yields (see Table I). Treatment of D-arabino-hexulose phenylosazone with CuSO, afforded two cyclization products, D-arabino-hexulose phenylosotriazole and aniline, in 68% yield and two hydrolysis products, D-arabinohexosulose and benzene, in 11% yield. Because of the low solubility of benzil bis-