Phenylhydrazones structure

Compound XXXII is an aldehyde-hemiacetal phenylhydrazone XXXIII is a hemiacetal-aWehydo phenylhydrazone and XXXIV is a so-called hemialdal structure. Of them, only XXXIII is suited to formation of a formazan. The successful formazan reaction furnishes proof of the predominance of this hemiacetal-oZde do phenylhydrazone structure. On these grounds, it is safe to assume that, to the oxidized polysaccharides themselves, this aldehyde-hemiacetal structure (or the hydrate form) is to be assigned. 

A wide variety of /3-lactams are available by these routes because of the range of substituents possible in either the ketene or its equivalent substituted acetic acid derivative. Considerable diversity in imine structure is also possible. In addition to simple Schiff bases, imino esters and thioethers, amidines, cyclic imines and conjugated imines such as cinnamy-lidineaniline have found wide application in the synthesis of functionalized /3-lactams. A-Acylhydrazones can be used, but phenylhydrazones and O-alkyloximes do not give /3-lactams. These /3-lactam forming reactions give both cis and /raMS-azetidin-2-ones some control over stereochemistry can, however, be exercised by choice of reactants and conditions. 

Indolization of 3-substituted phenylhydrazone 59 normally gives rise to two isomeric products, 4-substituted indole 60 and 6-substituted indole 61. The ratio of 60 to 61 from the cyclization depends on the nature of the R group, the structure of the carbonyl... 

Preliminary studies with a thio derivative of isatin (indole-2-thione-3-phenylhydrazone) also showed the hydrazone structure to be the favored tautomeric form (81JOC2764). 

XXII, for which they proposed the alternative name 1-phenyl-D-fructo-sone reaction with o-phenylenediamine produced a crystalline compound to which they assigned the structure XXIV, that is, 2-(D-orobwo-tetrahy-droxybutyl)-3-pheuylquinoxaline, the substituted osone reacting in the open-chain form XXIII. Compound XXIV, on treatment with phenylhy-drazine, yielded crystalline 2-formyl-3-phenylquinoxaline phenylhydrazone... 

Reactions of c -[Ru(bpy)2Cl2] with ligands (86) or (87) (X = CH2) in EtOH(aq) lead to [Ru(bpy)2(86)] + and [Ru(bpy)2(87, X = CH2)] respectively. When X = 0 in ligand (87), the product is the pyridine carboxylate complex [Ru(bpy)2(pyC02)], the structure of which is confirmed by X-ray crystallography. Complexes of the type [Ru(bpy)2L] " in which L represents a series of mono- and dihydrazones have been prepared and characterized by spectroscopic methods (including variable temperature H NMR) and a structure determination for L = biacetyl di(phenylhydrazone). When L is 2-acetylpyridine hydrazone or 2-acetylpyridine phenylhydrazone, [Ru(bpy)2L] + shows an emission, but none is observed for the dihydrazone complexes. The pyrazoline complex [Ru(bpy)2L] (L = 5-(4-nitrophenyl)-l-phenyl-3-(2-pyridyl)-2-pyrazoline) can be isolated in two diastereoisomeric forms. At 298 K, these exhibit similar MLCT absorptions, but at 77 K, their emission maxima and lifetimes are significantly different. ... 

The determination of the structure of a plant gum involves the establishment of its homogeneity, its equivalent weight, and rotation and its uronic acid and pentosan content by the well-known methods. The nature of the constituent sugars and the uronic acid are then determined, after hydrolysis of the gums, by ciystallization or by conversion into characteristic crystalline derivatives. As an example the hexose mannose may be identified as the free sugar or in the form of its anilide, methyl glycoside or phenylhydrazone. Autohydrolysis of the acid... 

Another type of substituted pyrazole is obtained by refluxing osazones with acetic anhydride during the acetylation, two molecules of water per molecule are removed. The structure of the resulting 5-(D-g/ycero-diacetoxyethyl)-3-formyl-l-phenylpyrazole 2-acetyl-2-phenylhydrazone (71) was determined by deacetylation followed by oxidation with (a) periodate to a pyrazolaldehyde (72), and (b) permanganate to the known l-phenyl-pyrazole-3,5-dicarboxylic acid (73), as well as by a study of its n.m.r. spectrum, which confirmed the pres-... 

It may well be, as Buckingham points out [104], that, at room temperature, under neutral conditions, and for a limited number of structural types, such as phenylhydrazones, no tautomeric shift to azo compounds takes place. The experimental facts are, however, that, under forcing conditions, aliphatic hydrazones have indeed been converted into azo compounds although often only in modest yield. 

NMR studies have confirmed the enol tautomer 19 for the so-called tetrahydroisatins,81 and support the hydrazone structure for N-methylisatin- 3-phenylhydrazone.242... 

A 2-deoxy-3-0-methylpentose (corchsularose) was isolated, as the crystalline phenylhydrazone, from corchsularin,11 a bitter principle from the alcoholic extract of jute seeds. According to this investigation, the structure of the pentose derivative was adequately corroborated by the isolation of methoxysuccinic acid after permanganate oxidation. It seems remarkable, however, that a 2-deoxypentose derivative should withstand the conditions of hydrolysis (concentrated hydrochloric acid) which were employed to liberate it. 

The base-catalyzed, / -elimination reaction of D-mannose phenyl-hydrazone is consistent with the acyclic structure for the phenylhydra-zone in solution. However, the small proportion of a nitroxide radical observed on treatment of the phenylhydrazone with a strong base may indicate the existence also of a fractional proportion in a cyclic structure in equilibrium with the open-ring structure, as was suggested by Blair and Roberts (43). The hydrazino moiety required for nitroxide-radical formation could be derived from the cyclic form of D-mannose phenylhydrazone in solution. 

The Fischer cyclization of phenylhydrazones of structure (18) gives rise to the carbinolamine-lactones (19). Reaction with methylamine, followed by reduction, then affords a short synthesis of esermethole (20a) and eserethole (20b) (Scheme... 

You should already be familiar with approximately half of the reactions listed in Table 9.2 from your introductory class. Moreover, you have probably tried to prepare an oxime, a phenylhydrazone, a 2,4-dinitrophenylhydrazone, or a semicarbazone. These compounds serve as crystalline derivatives with sharp and characteristic melting points for identifying aldehydes and ketones and for distinguishing them. When spectroscopic methods for structure elucidation were not available, such a means of identification was very important. 

The conversion of the synthetic 4-(/3-D-galactopyranosyl)-D-mannose (epilactose) through the hexaacetyllactal to lactose forms the keystone in the total synthesis of this sugar.61-62 Proof of the structure of 4-(/3-D-gal-actopyranosyl)-D-mannose was accomplished by hydrolyzing it with hydrochloric acid, and also with emulsin, to D-galactose (identified by oxidation to mucic acid) and D-mannose (identified as its phenylhydrazone).18... 

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