1.2- Dihydrazones

The aza analogue of 97, l,2,5,6-tetraaza-6fl-tellurapentalene 98, was isolated in very low yield (2%) as a product of reaction of Te02 with the dihydrazone of 1,3-cycloheptadione (79BSF205). 

The condensation of dihydrazones of aryl-substituted 1,2-diketones with aryl-substituted 1,2-diketones has also been described, albeit with rather low yields (up to 15 %).20 Subsequently, it was explicitly shown that this reaction leads to the same products as the dimerization of benzil monohydrazones, i.e. the 1,2,5,6-tetrazocine system, is not produced, rather the bicyclic tetraazapentalene system is obtained,21... 

The vicinal dihydrazones formed from monosaccharides with arylhydrazines have been called arylosazones, but are preferably named as ketoaldose bisfphenylhydra-zone)s... 

S-Tetrazin. Das bei der Reaktion von s-Triazin und Hydrazin entstehende i. 2-Diformylhydrazin-dihydrazon (XLIV) ist eine... 

A different example of this general type involves the ds-dihydrazone complex (64). This complex is prepared by condensation of the corresponding dialdehyde with hydrazine in the presence of nickel or copper ion (Curtis, Einstein Willis, 1984). The two uncoordinated -NH2 groups react with a ketone or a diketone such that cyclization occurs in each case [2.8], In these systems, the pendant -NH2 groups are expected to be reactive since their non-coordination results in the respective nitrogen lone pairs being readily available for nucleophilic reaction. 

As shown in Scheme 19, dihydrazone gives a monoselenoketone, probably a diselenoketone that dimerizes, and 1,3,4-selenadiazoline.218... 

Benzidine, N,N -diethyl-, 36, 21 Benzidine dihydrochloride, 36, 22 Bcnzil, 34, 42 Benzil dihydrazone, 34, 42 Benzilic acid, 33, 37 2-Benzimidazolethiol, 30, 56 l,2-Benzo-3,4-dihydrocarbazole, 30, 91 Benzofuran, 3-methyl, 33, 43 Benzofurazan oxide, 31,14, 15 37,1 Benzoguanamine, 33,13 Benzoic acid, 32, 94 37, 21 Benzoic acid, -acetyl-, methyl ester, 32, 81... 

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. ... 

All initiators are potentially explosive compounds and must be stored and handled with care. 2,2 -AIBN is obtained from the reaction of acetone with potassium cyanide and hydrazine hydrochloride. As shown in equation 17.51, the reaction produces hydrogen cyanide and hydrazine. The latter reacts with acetone forming acetone dihydrazone, which reacts with... 

From what was plarmed as a straightforward displacement of the chloride atom in 36 with hydrazine followed by a condensation with 2-tetralone and Fischer indolization to produce 39, dihydrazone 38 was isolated as an intermediate, resulting fi om dihydrazine 37 <99JHC441>. Subsequent Fischer indole cyclization and aminolysis of 38 produced 39 a mono-hydrazone intermediate (as opposed to 38) was ruled out by the authors on the basis of H NMR. 

A solution of 105.1 g. (0.5 mole) of benzil (Note 1) in 325 ml. of w-propyl alcohol is prepared in a 1-1. round-bottomed flask which is fitted with an efficient reflux condenser. To this solution 76 g. (1.30 moles) of 85% hydrazine hydrate (Note 2) is added, and the mixture (Note 2) is heated under reflux for 60 hours. The solution is cooled with an ice bath, and the benzil dihydrazone is separated by suction filtration. The crystals are washed with 200 ml. of cold, absolute ethanol and dried (Note 3) on the suction filter for 1 hour. The yield of benzil dihydrazone is 99-106 g. (83-89%), m.p. 150-151.5°. 

Benzil dihydrazone should not be dried in a vacuum desiccator, for it sublimes easily. 

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