Bishydrazone structure

Another controversial aspect of the bishydrazone structure concerns the hydrazone residues. The bishydrazone was proposed to have the structure 46, which mutarotates in solution to 47 (47). More recently, on the basis of a comparative study of the spectroscopic properties of the bis(phenylhydrazone) with some related compounds, the bishydrazone was assigned the structure 2,3-dideoxy-3-phenylazo-2-phenylhydrazino-L-threo-hex-2-enone-l,4-lactone (48) (48). However, this latter structure was inconsistent with its NMR spectra (49). 

Different results, depending on the structure of the initial 2-benzopyry-lium salt, were obtained also in reactions with phenylhydrazine. Thus, the 1,3-dimethyl-substituted cation 35 is converted into an isoquinolinium salt 174(R = Ph)(70KGS1308), whereas the 1,3-diphenyl derivative 178 forms an indole 180 via the bishydrazone 179 by the Fischer reaction (71CB2984). 

The bishydrazones of DHA and related compounds have been studied and used to synthesize a number of nitrogen derivatives of DHA (18-23), Thus the bisphenylhydrazone of DHA is reduced by hydrogen/platinum to 2,3-diamino-2,3-dideoxyascorbic acid, which in turn can be converted to a variety of acyl derivatives. The structure of DHA phenylosazone is a hexenonelactone (24),... 

The same authors82 suggested a mechanism for the reaction of 1,4-dicarbonyl compounds with monosubstituted hydrazines, which affords, depending on reaction conditions and structural factors, the mono- and bishydrazones, N-aminopyrroles, and 1,4-dihydropyridazines. Some relatively simple 1,4-dihydropyridazines (31) were prepared by condensation of monosubstituted hydrazines with succinic or levulinic aldehyde.83... 

The structure of inosose bis(phenylhydrazones) resembles that of saccharide osazones in that the bishydrazone residues in both are chelated that is, bridged by an imino group (the other NH group is unchelated). 

Within the last two decades, a number of chemical structures have been proposed as metal deactivators for polyolefins. These include carboxylic acid amides of aromatic mono- and di-carboxylic acids and N-substituted derivatives such as N,N -diphenyloxamide, cyclic amides such as barbituric acid, hydrazones and bishydrazones of aromatic aldehydes such as benzaldehyde and salicylaldehyde or of o-hydroxy-arylketones, hydrazides of aliphatic and aromatic mono- and di-carboxylic acids as well as N-acylated derivatives thereof, bisacylated hydrazine derivatives, polyhydrazides, and phosphorus acid ester of a thiobisphenol. An index of trade names and suppliers of a few commercial metal deactivators is given in Appendix A4. 

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