Bishydrazone reactions

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). 

In some cases a whole series of dehydrogenation reactions may proceed sequentially to yield aromatic or highly conjugated products. An example of this is seen in the aerial oxidation of the nickel(n) complex of the macrocycle formed by the template condensation of biacetyl bishydrazone with formaldehyde. The product of the oxidation is the fully aromatic dianionic macrocyclic complex (Fig. 9-24). 

If a very reactive cycloalkyne is synthesized, the necessary fast reaction at low temperature, must be worked up in a short period. These conditions are met by the oxidative decomposition of bishydrazones with lead tetraacetate in dichloro-methane. By this method the most strained, but still isolable cycloalkyne 3,3,7,7-tetramethylcycloheptyne (10) was prepared8), which on standing at room temperature... 

The reaction of 1,2-dibromocycloalkenes (13) with magnesium in the presence of l,3-diphenylbenzo[c]furan (16) affords a cycloalkyne adduct (17). Also, the mercuric oxide oxidation of bishydrazone, which has been used extensively in the preparation of open-chain and medium or large cyclic acetylenes " , is adapted for small ring bishydrazones (18) . Treatment of 18 with mercuric oxide in the presence of 16 or of phenyl azide results in the adducts, 17 and 19, respectively. It seems... 

Table 1. Yields of cycloalkyne adducts. I Grignard reaction II oxidation of bishydrazone III base elimination of bromomethylene derivative IV oxidation of aminotriazole V photolysis of tosylaminotriazole anion...

The nitrogen derivatives of L-ascorbic acid or its dehydro derivative, and the rationale for interest in these derivatives, are reviewed. In particular, the reactions of dehydro-L-ascorbic acid (DHA) with o-phenylenediamine or its substituted derivatives are surveyed as well as the reactions of DHA with hydrazines, which yield monohydrazones or bishydrazones. Further conversion of these initial derivatives into a variety of nitrogen heterocyclic compounds is evaluated. The reactions of i.-ascorbic acid with amino acids are also examined. 

The reaction of 38 with various hydrazines gave the corresponding mixed bishydrazones (42), which could be rearranged into other heterocycles (25,26), The bishydrazones could not be isolated with... 

Treatment of DHA or 38 with the corresponding arylhydrazine afforded the bis(arylhydrazone) (41) (33-40), Similarly, aroylhydra-zines and semicarbazide condensed readily with DHA to give the corresponding bishydrazone (41,42) and bis(semicarbazone) (43,44), A series of derivatives related to sulfa drugs (45) was prepared by the reaction of DHA with hydrazines having such moieties. 

The bishydrazones are now known to be in the 1,4-lactone form, showing that no opening of the lactone ring in DHA occurred during the reaction. However, at one time (38) the 1,5-lactone was the preferred form, since the IR spectra of the bishydrazones showed a carbonyl lactone band at a frequency lower than that expected for a... 

Cyclization of a variety of bishydrazones of a,)3-diketoacids,52,285 a,j8-diketoesters52,264 397,732,782 and a,j3-diketoamides,352 using either acid, base or heat, to 4-arylazo-2-pyrazolin-5-ones has been reported (eq. 184). In this reaction the aryl groups have usually been the same... 

Bishydrazones 126 and 127, unsubstituted at the nitrogen atoms, on oxidation immediately form 1-amino-1,2,3-triazoles in 20-60% yields [Eqs. (34) and (35)] (61CB3260 71JPR882). For 127, the reaction is sensitive to steric hindrance, and the formation only of l-amino-4-aryltriazoles is the evidence for this. 

The reaction between some 1,4-diketones and 2,4-dinitrophenylhydrazine has been reinvestigated a mixture of bishydrazones and the corresponding N-(2,4-dinitroanilino( pyrroles is formed. With diethyl a, -diacetylsuccinate, in addition, a pyridazine derivative was formed. ... 

Benzoylhydrazones of 2,2-dimethyl-4,4-diphenylbut-3-enal undergo a novel photochemical cycli-zation to afford A -pyrazolines (l-benzoyl-4,4-dimethyl-5-diphenylmethyl) <93CC72l>. Prinzbach has described an interesting series of reactions <93CB429> starting from the bicyclic dienedione (237), the addition of hydrazine yields the double-Michael adduct (238) (and not the bishydrazone). which is cyclized into the double-A -pyrazoline (239) for, finally, obtaining the desired double-A -pyrazoline (240) (to prepare iron-tricarbonyl complexes). 

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... 

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