Hydrazone from

On the contrary, the preparation of hydrazones from the monoacetals of gyloxal is a straightforward process4. b Only one of two possible isomers (Z- or E-isomer) is detectable . 

Dinuclear cyanines, see Thiazoiocyanines 2,2 -Dioxo-A-3,3 -biselenazol-5.5 -inylidene-bis hydrazones, from 2-hydrazino-selenazoles, by oxidation with FeCl3 and H,Oj, 252... 

Compound NPYR Species Rat Tissue Preparation Liver microsomes Comments identification of 4-hydroxybutyr-aldehyde (as its 2,4-dinitrophenyl-hydrazone) from a-hydroxylation Reference 9... 

The formation of hydrazones from the corresponding carbonyl compounds has been accomplished initially in toluene [79]. The treatment of hydrazone with alkali (KOH) accomplishes Wolff-Kichner reduction that proceeds in good yield under... 

The reason for the rate increase in the presence of phenylhydrazine remains unclear. The authors note that phenylhydrazone also accelerates the reaction and that the formation of the hydrazone from the solvent (acetone) cannot be ignored. Phenylhydrazine is known to reduce Cu(II) to Cu(I) (115), and the authors observed that the hydrazone is also capable of this reduction. It is interesting that the same rate acceleration could not be induced by other amine bases such as pyridine, l,5-diazabicyclo[4.3.0]non-5-ene (DBN), or DBU. While it is likely that phenyl-hydrazine-phenylhydrazone accelerates the slow step of the catalytic cycle through some sort of interaction with the metal, the exact nature of this involvement remains unclear. Elucidation of its role in the reaction may greatly aid the development of this transformation, and it is expected that it will impact the ultimate solution to this problem. 

Hydrazones from a-ketoesters and diazonium salts with the acid of base. 

Thermodynamic template reactions allow the formation of hydrazones from hydrazines and carbonyl compounds, in the same manner as simple imines are formed. However, in many cases it is more convenient to form hydrazones in non-template reactions, as they are generally easier carbonyl derivatives to isolate than are simple imines. Hydrazone complexes often are capable of further manipulation and both aspects of synthesis and reactivity will be combined in this section. 

Scheme 7.4 Mechanism of the preparation of hydrazones from azides.

Metal-Complex (Formazan) Dyes. The hydrazone from 2-carboxyphenylhydra-zine-4-sulfonic acid and benzaldehyde is suspended in water and then dissolved by adding aqueous sodium hydroxide to obtain pH 6.5 -7.0. This solution is added to the aqueous diazonium salt solution obtained from a typical aqueous diazotiza-tion of 4-(2-sulfooxyethylsulfonyl)-2-aminophenyl-6-sulfonic acid. The mixture is then dripped into an aqueous solution of copper sulfate, while the pH is maintained with soda at 5.5 - 6.5. After complete coupling the pH is adjusted to 1 with concentrated hydrochloric acid. The strongly acidic solution is then neutralized with alkali to pH 5.5. The copper - formazan complex is salted out along with sodium chloride, filtered, washed with dilute aqueous sodium chloride solution, and dried. A dark powder results which gives a dark blue solution in water. It consists of an electrolyte-containing powdered sodium salt of the acid 25 ... 

Diazaphospholes 4 and 5 are colorless to pale yellow distillable liquids or crystalline solids that are stable to oxidation by air and do not react with elemental sulfur. They are readily hydrolyzed to give the hydrazone from which they originate and phosphorus acid. While only a few reactions of 1/7-1,2,3-diazaphospholes 4 are reported, the chemistry of the 2//-isomers 5 is well studied. In CHEC-II(1996), the following reactions of 1,2,3-diazaphos-pholes are described in detail N-protonation and alkylation, polar addition to the P=C bond and substitution at C-4, cycloaddition reactions, substituent reactions, and the formation of transition metal complexes <1996CHEC-II(4)771>. 

Other imino derivatives arise, as by-products or in side reactions, on heterocyclization. Thus, the treatment of cinnamoyltropolones 75 with hy-droxylamine (Scheme 19) yields, in the case of the 5-nitro derivative, the corresponding isoxazolotroponeoxime (89JHC371). The formation of oximes and several hydrazones from 3-acetyltropolone or its derivatives has also been mentioned (Section II,A,3,c). Moreover, an azine was obtained in addition to quinoxalotropone 213 (Section II,B,2,c) a tropone immonium salt was isolated after an extremely complex diene reaction of an 6-amino-2-azaazuIene (93CB441). 

A versatile and efficient synthesis of 3-substituted-l//-indazoles 199 is based on the generation and subsequent cyclization of the intermediate hydrazones from aryl mesylates 198 and hydrazines (Scheme 119) <1999S588, CHEC-111(4.01.9.1.2)94>. 

With benzylic halides, the elimination requires sodium hydride in hot DMF, whereas aliphatic substrates do not undergo elimination at all. This drawback was surmounted by the use of N-4-acetoxyphe-iiyltrifiamide. 3 Elimination now occurs via the quinoneimines under mild conditions, even with aliphatic substrates (Scheme 17). Despite the ingenious chemistry, there appear to be few advantages over other methods. A procedure exists for the synthesis of hydrazones from halides (Scheme 18). ... 

Derivatives of hydrazine (R NH NH2) react with ketones to form substituted hydrazones of general formula (i). These compounds cannot suffer elimination of nitrogen because the intermediate diimides would be disubstituted, and therefore could not give anions. The effect of forming a substituted hydrazone from an a -substituted ketone is to promote... 

JAPP KLINGEMANN Hydrazone Synthesis Synthesis of hydrazones from diazonium salts and an activated methylene group (or enamlne)... 

A final method of alkene formation from a-derivatized ketones entails formation of unsaturated tosyl-hydrazones from a,P-unsaturated ketones followed by conjugate reduction with sodium cyanoborohy-diide in acid media. This transformation, which proceeds with regioselective migration of the original double bond, has been applied to the synthesis of quassinoids by Ganem et al. (Scheme 22). A similar... 

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