Pyrazole Synthesis from 1,3-dicarbonyls

K N O R R Pyrazole Synthesis Pyrazole synthesis from a -dicarbonyl compourxi arxi a hydrazine. 

Pyrazole synthesis from a p-dicarbonyl compound and a hydrazine (see 1st edition). 

The synthesis of pyrazolcs starting from a hydrazine and a 1,3-dicarbonyl compound is a well established reaction in organic synthesis. If a mono-suhstituted hydrazine is reacted with an unsymmctrically substituted 1,3-dicarbonyl compound, two different pyrazole products which arc regioisomers could he formed (sec figure 10.3-2). 

Organic synthesis 72 [OS 72] Pyrazole ring closure from 1,3-dicarbonyl compounds and hydrazines... 

Another interesting synthesis started from A-acylglycine esters which generated A-acylimino esters in situ following bromination and base treatment. When these A-acylamino esters were alkylated with 1,3-dicarbonyl compounds and hydrazines, the corresponding pyrazoles were formed (Scheme 18) (88T5403). 

In planning the synthesis of a pyrrole or a pyridine from a dicarbonyl compound, considerable variation in oxidation state is possible Tire oxidation state is chosen to make further disconnection of the carbon skeleton as easy as possible. We can now see how these same principles can be applied to pyrazoles and pyridazines. 

The synthesis of 3,5-bis(trideuteromethyl)pyrazole was achieved by reaction of perdeuterated acetylacetone with perdeuterated hydrazine hydrate <90MI 30l-02>. Preparation of [ NjJpyrazoles was achieved from commercial NH2- NH2 and -dicarbonyl compounds or the corresponding acetals <89JA7304, 92JA9657, 92JCS(P2)1737>. 

Reactions of heterocycles ch29 How to make pyridazines and pyrazoles How to make pyrimidines from 1,3-dicarbonyl compounds and amidines How to make thiazoles How to make isoxazoles and tetrazoles by 1,3-dipolar cycloadditions The Fischer indole synthesis Making drugs Viagra, sumatriptan, ondansetron, indomethacin How to make quinolines and isoquinolines ... 

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