Aldehydes with hydrazine

A useful method for obtaining indazoles in high yields involves treatment of ortho-azido phenyl ketones or aldehydes with hydrazine hydrate. When this reaction was applied to 3-azido-2-formylselenophene, selenolo[3,2-c] pyrazole (111) was obtained in low yield. The yield could not be improved when the amino derivative was prepared as an intermediate142 (Scheme 13). 2-Dialkylamino-5-formylselenophenes react with diazonium salts under deformylation conditions to give azo dyes (Eq. 39).143 Another nitrogen-containing derivative of selenophene is compound U2.144 ... 

Reaction of aldehydes with hydrazine, or mono- or 1,2-disubstituted hydrazines is the method used almost exclusively for the preparation of hexahydro-l,2,4,5-tetrazines (377). All types of hydrazines have been used hydrazine itself, monoalkyl-, monoaryl-, dialkyl-, diaryl-, alkylaryl-, alkylacyl- or arylacyl-hydrazines. The aldehydes used were mainly aliphatic aldehydes. An excellent review by Wiley of the literature on this reaction up to 1974 is available (78HC(33)1075, p. 1190). 

Reaction of aldehydes with hydrazine followed by catalytic oxidation of the hexahydro-... 

KISHNEK CYCLOPROPANE SYNTHESIS. Formation of cyclopropane derivatives by deeompoxiiion of pyra/olines formed by reacting tr/l-unsiiiurated kelones or aldehydes with hydrazine. 

Thiadiazolidines can be obtained from aliphatic aldehydes or ketones and disubstituted hydrazine derivatives (Scheme 29). A typical preparation of a mesoionic compound consists in the reaction of 1-methylthioacylhydrazine and phosgene (Scheme 31a). Syntheses by three-bond formation are rare for example, a one-pot reaction of an aldehyde with hydrazine and sulfur. A typical ring transformation reaction is the irradiation of 1,3,4-oxadiazoles to yield 1,3,4-thiadiazoles. 

A compound containing the C=N—NH2 group, formed by the reaction of a ketone or aldehyde with hydrazine, (p. 853)... 

Rieaction of the ketone or aldehyde with hydrazine yields a bydrazone in the normn way ... 

Colorometric procedures involving reaction of aldehydes with hydrazines, semicarbazide, or piperidine/nitroprusside solutions are also non-specific and lack sensitivity (15, 35, 36). Schmidt et al. (33) have proposed an HPLC method for analyzing the 2,4-dinitrophenylhydrazone (DNPH) derivatives of specific aldehydes. This procedure allows for a number of ddehydes to be separated and measured simultaneously, however, HPLC methods in general suffer from poor resolving power and may have low sensitivity (37). In addition, hydrazine derivatizations are often performed under acidic conditions for maximal reactivity these conditions would not provide quantitative information on total aldehyde content. 

Methods for the preparation of hydrazones and oximes differ little from those used for the synthesis of imines from ketones and aldehydes in that the appropriate nitrogen species and the ketone are mixed. However, the equilibrium for the majority of reactions of ketones and aldehydes with hydrazines and hy-droxylamine favor the product hydr nes and oximes and removal of the water formed by the condensation is not required. 8(> Acid catalysis is complicated by the basicity of the reagent and, for example, the maximum rate of oxime formation is at approximately pH 4. Complicating reactions can occur such as the 1 2 combination of hydrazine with two ketones or aldehydes to form azines but this is not a problem with the substituted hydrazines that are used for asymmetric induction. 

The parent pyrido[3,4-tf]pyridazine (15) is obtained by condensation of pyridine-3,4-dicarb-aldehyde with hydrazine.3,57 [4-2H]]Pyrido[3,4-r/]pyridazine can similarly be prepared.129... 

Reaction of aldehydes with hydrazine affords hexahydro-l,2,4,5-tetrazines 1 in high yield. These are oxidized with oxygen in the presence of platinum(IV) oxide to l,6-dihydro-l,2,4,5-tc-trazines 2. Final oxidation of 2 with nitrous acid affords 1,2,4,5-tetrazines 3.213,215... 

A useful variant of the inline-forming reaction just discussed involves the treatment of a ketone or aldehyde with hydrazine, H2NNH2, in the presence of KOH. This reaction, discovered independently in 1911 by Ludwig Wolff in Germany and N. M. Kishner in Russia, is a valuable method for converting a ketone or aldehyde into an alkane, RjOO — RjCHj. The Wolff-Kislmer reaction was originally carried out at temperatures as high as 240°C, but a modification in which dimethyl sulfoxide is used as solvent allows the process to take place near room temperature. 

A brief description has been given [74] of the reaction of an aldehyde with hydrazine hydrate in the presence of potassium cyanide ... 

Formation of cyclopropane derivatives by decomposition of pyrazolines formed by reacting a,(3-unsaturated ketones or aldehydes with hydrazine ... 

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