Osazones glycosuloses from

Fischer suggested that the phenylhydrazone (1), first formed from an aldose and phenylhydrazine, is oxidized with phenylhydrazine to (2), the glycosulose l-(phenylhydrazone) [glycosone l-(phenylhydrazone)], which reacts with a third molecule of phenylhydrazine to form the osazone (3). 

An interesting intermediate, possibly deriving from Weygand s Scheme B, was isolated by Haas and Seeliger from the reaction of u-glucose with phenylhydrazine in acetic acid or hydrochloric acid. This product is 3-(D-fflrol)fno-tetrahydroxybutyl)cinoline (30), produced, not by the hydrolytic decomposition of the osazone, but by the cyclization of the intermediate glycosulose 2-(phenylhydrazone) (28) or the aldimine 2-(phen-ylhydrazone) (29). 

Indirect evidence for the possible existence of cyclic forms of an osazone in solution appears from the different ways in which the osazones and their acetates react with nitrous acid, yielding the glycosulose in the first case and the osotriazole in the second. An explanation of this behavior was provided by the assumption that the osazones exist as equilibrium mixtures composed mainly of the acyclic form but also containing a small proportion of the cyclic forms (54). The glycosulose (55) was considered to be produced by the more rapid interaction of nitrous acid with the cyclic form, causing the equilibrium to shift in that direction imtil completion of the reaction, whereas the osotriazole (57) was thought to be produced by the interaction of nitrous acid with the acyclic form (56) of the acetate, which is incapable of cyclization. 

A large number of glycosulose l-(2-substituted) hydrazones have been prepared by Henseke and coworkers from the osazones by action of nitrous acid. These products, such as (89), were then treated with other substituted hydrazines, to give mixed osazones," or with hydrazine and other carbonyl reagents, to obtain ketazines and azines" hydrazone thiosemicarbazones, and hydrazone oximes. ... 

Hexosulose hydrazones and the mixed osazones react with diazotized aniline to give formazans, and with hydrogen peroxide to give pentonic acids. Unlike the mixed osazones obtained by transhydrazonation, the derivatives obtained from the glycosulose hydrazones are pure, uncontaminated compounds, and the positions of their hydrazone residues are well established. Thus, they afford remarkable possibilities, not only in the preparation of new types of compound, but also in enabling the reaction of osazones to be followed more closely, as in the case of triazole formation," and in studying the structure of anhydro-osazones. ... 

Furthermore, he used the reaction to obtain a number of mixed osazones these compounds are, however, best prepared from the glycosulose hydra-zones. A detailed study of transhydrazonation was made by Mandel, who confirmed VotoCek s finding that the reaction proceeds best when the products have low solubilities, as with the (nitro- and dinitro-phenyl)-osazones. 

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