Hydroxy aldehydes reaction with hydrazines

The coupling of enals and glyoxals was realized by hydrogen-mediated reaction with the cationic Rh complex and PI13P [35]. The intermediate aldehyde enolates derived via Rh-catalyzed hydrogenation were trapped with glyoxals to form (l-hydroxy-y-kclo-aldchydes, which were treated sequentially with hydrazine to give pyridazines in a one-pot transformation to provide, for example, a 62% yield of 72 (Scheme 21). 

Both the hydroxy aldehydes or aldehyde alcohols and the hydroxy ketones or ketone alcohols undergo the characteristic aldehyde and ketone reactions due to the carbonyl group. They react with hydrogen cyanide, phenyl hydrazine and hydroxyl amine. These reactions have been discussed in connection with the aldehydes (pp. 116, 224) and will be considered again when we study the carbohydrates. The carbohydrates in fact belong here with these hydroxy aldehyde and hydroxy ketone compounds but on account of other relations they are better considered at a later time. 

Maleic anhydride and hydrazine give the hydroxy-pyridazinone ( maleic hydrazide ) directly, " the additional unsaturation in the 1,4-dicarbonyl component meaning that an oxidative step is not reqnired conversion of 3-hydroxypyridazin-6-one into 3,6-dichloropyridazine makes this useful intermediate very easily available. Mucohalo acids (18.1.1.4), synthons for 4-carboxy-aldehydes, are an oxidation level down and produce l-aryl-pyridazin-3-ones on reaction with arylhydrazines. ... 

Reaction of 2-chloro 3-substituted quinoxalines 22 with hydrazines provides another simple preparation of pyrazolo[3,4-h]quinoxalines. The parent heterocycle 23 has been obtained by treating the aldehyde 22 (R = CHO) or the dibromomethyl derivative 22 (R = CHBr2) with hydrazine. Similarly the nitrile 22 (R = CN) has given the 3-amino compound 24 in 72% yield, and methylhydrazine with the ester 22 (R = COjEt) gave the 3-hydroxy derivative 25. In spite of the ready cyclization of the aldehyde 22 (R = CHO) with hydrazine, the corresponding... 

The 1,2,4-triazine 4-oxides 55 were synthesized by the reaction of nitrones 158 (generated from a-hydroxylamino ketones and aldehydes) with an excess of hydrazine, followed by the oxidation of the intermediate 4-hydroxy-2,3,4,5-tetrahydro-l,2,4-triazines 159 with lead(TV) oxide (73KGS134). 

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