Pyrazolinone synthesis

Carpino et al. recently disclosed the synthesis of the fused pyrazolinone-piperidine dipeptide 56 with potent growth hormone secretagogue activity. The synthesis of the intermediate pyrazolone was accomplished by reacting the ketoester 54 with methyl hydrazine in refluxing ethanol. ... 

A simple three-step synthesis of diazabicyclo[3,3,0]octadienes from o-keto esters via pyrazolinones 185 and halopyrazolinones 186 is known... 

Kost and Sagitullin,531 Fridel and Combes,532 Domnin,833, 534 and Kauffmann5340 For the synthesis of pyrazoles consequent on the formation of an N—N link, see Belov,45 Fowden,130 Brian et al.,300 and others.306,535,536 A number of pyrazoles have been prepared from pyrazolinones see, for example, Michaelis and Lachwitz537 or Mustafa and co-workers.53 7a... 

Various pyrazole systems having appropriate substituents in the 5-position can be converted into pyrazolinones. The most frequently used synthesis of this type is hydrolysis of 5-alkoxypyrazoles which is shown with others in eqs. 18-21. 

A rather unusual synthesis of pyrazolinones from a cyclobutane... 

Advances in the synthesis of pyrazolo[3,4-l ]pyridines 12COC400. Chemistry of pyrazolinones and their apphcations 12COC373. l-Cyanoacetyl-3,5-dimethylpyrazole Effective cyanoacetylating agent and a new building block for the synthesis of heterocyclic compounds 12KGS1216. 

Perumal has described a four-component sequential protocol that allows the synthesis in good yields of antitubercular 2-aryl-5-methyl-2,3-dihydro-l/f-3-pyrazolones 18 from atylhydrazines, methyl acetoacetate, aromatic aldehydes and 5-naphthol in the presence of / -TSA in water under reflux conditions [13], The reaction proceeds by an initial acid-catalyzed cyclocondensation of the hydrazine and dicarbonyl components to give pyrazolinone 19. A parallel acid-catalyzed condensation between p-naphthol and the aromatic aldehyde affords the intermediate quinone methide 20, and Michael addition of the enol form of 19 onto the exocyclic double bond of 20 furnishes the final product (Scheme 1.9). 

Condensation of resin bound ketones with hydrazines followed by cyclizative cleavage was used in a synthesis of pyrazolinones [67]. Samarium iodide induced radical cyclization of allyl aryl ethers led to benzofuran derivatives [68]. Kurth et al. have reported a two reaction iterative process for the construction of polyisoxazolines [69] and polyisoxazoles [70]. An intramolecular Heck reaction has been employed to prepare 2-oxindole derivatives [71]. 

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