Pyrazolols

The F-triazole ring in the pyrazolol 3,4-d)-i -triazole (90) was generated by nitrosation of 4,5-diamino-3-methyl-l-phenylpyrazole.86... 

Pyrazolol 3,2-c] -s-triazole (199) was isolated in low yield (1%), along with the tetrazolylpyrazole (200), when 3(5)-pyrazole diazonium chloride was treated with one equivalent of diazomethane.207... 

Tosylpyrazolines (56) stereoselectively react with trimethylaluininuin to afford pyrazolols (57 equation 26). ... 

Indazolo[2,l-fl]indazole (dibenzo[i,/]-3a,6a-diazapentalene) IV,B,2 Pyrazolol l,2-a]benzotriazole (benzo[A]-l,3a,6a-triazapentalene) ... 

Pyrazololl,5-c][l,3,5]triazines have been evaluated as inhibitors of the photosynthetic electron transport chain at the photosystem II level. Some of the compounds exhibited remarkable inhibitory activity <04MI1898>. 

For ketoester the substrate, the hydrazone forms exclusively between the hydrazine and with more active ketone. The corresponding hydrazone-ester then cyclizes to produce the pyazolone. Mechanistically, the more basic and less substituted hydrazine amine condenses with the ketone. The resultant hydrazine-ester then cyclizes to the pyrazolol, which could also tautomerize to the corresponding pyrazolone. 

In addition to the conventional method of making pyrazolones using keto-ester, diethyl 2-(ethoxymethylene)malonate could be used as a surrogate for the keto-esters. As shown below, treatment of phenylhydrazine with diethyl 2-(ethoxymethylene)malonate in ether gave rise to pyrazolols, which was acylated with acyl chloride. The pyrazolols/pyrazolones served as intermediates for the preparation of a potent multi-drug resistance modulator. ... 

Finally, pyrazolol/pyrazolone derivatives have recently been synthesized as inhibitors of Mycobacterium tuberculosis and as potent antihyperglycemic agents. ... 

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