Hydrazone oxide

Table 2 Syntheses of [1,2,4]triazolo[4,3-a]pyridines by means of hydrazone oxidation ...

Heterocyclic hydrazones, oxidative coupling of, 9 360 Heterocyclic ligands, thorium and,... 

The oxidation of aromatic phenylhydrazones leads to cis azoxy compounds. At one time, these products were designated hydrazone oxides, but more recent work has established them as azoxy compounds. Aliphatic hydrazones give more complex oxidation products. At low temperatures, azoxy compounds form at reflux temperatures, hydrazides are isolated. 

As indicated before, cis azo compounds may be oxidized to cis azoxy compounds, and certain hydrazones also may be oxidized to cis azoxy compounds (hence the old but incorrect designation hydrazone oxides ) [7]. 

Diazo compounds have previously been prepared by a variety of methods. Some of these methods Include hydrazone oxidations, the reaction of diazomethane with acid chlorides,4 the reaction of activated methylene compounds with tosyl azide, decomposition of N-nitroso compounds, ... 

Oxidative Coupling of Azole Hydrazines with Hydrazones. Oxidative coupling of azole hydrazines with hydrazones takes place spontaneously in the presence of pyridine in air and is confined to the synthesis of heteroarylformazans, for example, 33 [66] ... 

Diazomethan Dicyan- IV/3, 519 (Hydrazon-Oxid.) El4b, 1139 (Hydrazon-Oxid.) E19b, 1204 (Hydrazon-Oxid.)... 

Tricyclo 2.2.0.01>s hexan 2-Diazo-3-oxo-l,4,5,6-tetramethyl- E14b, 1135 (Hydrazon-Oxidation)... 

Freeman employed an extension of the Iffland hydrazone oxidation in a new synthesis of cyclopropyl acetates. An i>, -unsaturuted ketone is condensed with hydrazine to form a 2-pyrazolina, as formulated fur the conversion of mesityl oxide... 

Hydrazones.—Oxidation of hydrazones with lead tetra-acetate gives nitrogen and a mixture of acetates and olefins, apparently through the intermediacy of diazo- and diazonium compounds (Scheme 18). The steroid hydrazone at C-7 affords mainly the 7a-acetoxy-derivative, but at C-3 a mixture of 3a- and 3j8-acetoxy-compounds results, together with an olefinic fraction. ... 

Ox = metal oxides and various other oxidants for hydrazone oxidation. 

The asymmetric hydrogenation of imine derivatives that contain a second ligating functionality to create two-point binding of the substrate have been investigated. Reactions of two types of such substrates are shown in Equations 15.85 and 15.86. In the first example, an aroyl hydrazone undergoes selective hydrogenation to form the enantioenriched N-alkyl hydrazone. Oxidative cleavage of the N-N bond then leads to the primary amine. 

Catalysis of Diazoalkane-Carbonyl Homologation. How New Developments in Hydrazone Oxidation Enable the Carbon Insertion Strategy for Synthesis... 

Hydrazone oxidation by hypervalent iodine finds precedent in the literature [154-157], but until now has not enjoyed much in the way of generality. Recently, Myers and Furrow [17] reported the use of A-ferf-butyldimethylsilylhydrazones (TBSHs)... 

Chlorodimethylsulfonium chloride (Swem reagent) represents another metal-free alternative for hydrazone oxidation [54]. The strategy was discovered by chance during research on a new conversion of free hydrazones to alkyl chlorides [159]. When benzophenone hydrazone was exposed to Swern reagent in the absence of an amine base, Brewer and laved observed localized yet transient red coloration of the reaction mixture. Diligent experimentation then led to the... 

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