3- Amino-5-methylpyrazol, reaction with

Petrov AA, Emelina EE, Sehvanov SI (2008) a-Aminoazoles in synthesis of heterocycles IV. Regiodirection of 3(5)-amino-5(3)-methylpyrazole reaction with hexafluoroacetylacetone. Russ J Org Chem 44 263-269... 

The preparative route to [l,5-f][l,3,5]thiadiazine-2-ones 312 is outlined in Scheme 65. Thus, 5-amino-3-methyl-pyrazole-l-carbothioamides 313, obtained from the reaction of 5-amino-3-methylpyrazole (314) with isothiocyanates, react smoothly with trichloromethyl chloroformate to afford 312 (Scheme 65) <2004JFA1898>. 

Interestingly, when 5-amino-3-methylpyrazole reacted with Meldrum s acid and benzaldehydes in aqueous PEG 400, pyrazolo[3,4-fc]pyridines 129 were formed with good yields (Scheme 74) [105]. In the model reaction, it was demonstrated that the solvent can be recycled for up to five nms with limited decrease of yields. The reaction was foxmd to be regioselective and the structure of the products was xmambiguously confirmed by X-ray crystallography of 129 (R=4-OMe). This reaction was also successfully performed using n-butyraldehyde instead of benzaldehydes. 

Amino-5-trifluoromethyl-177-pyrazoles were synthesized by cyclocondensation reactions of 4-amino-4-ethoxy-1,1,1-trifluorobut-3-en-2-ones with hydrazines <2006S1485>. / -Alkoxyvinyl trifluoromethyl ketones 555 reacted with methylhydrazine to yield 3-(trifluoromethyl)-l-methylpyrazoles 556 (Equation 113) <2003JHC1087>. 

For example, Sandmeyer reaction on 3-amino-1-methylpyrazole yields the chloride 69. This compound when treated with chlorosulfonic acid followed by rerr-butylamine, provides the sulfonamide 70. The sulfonamide may be deprotected (TFA) and coupled to give the corresponding sulfonylureas. Alternatively, the rerr-butyl sulfonamide can be used to direct metalation to the 5 position (e.g. 73 —> 74)05). 

Pyrazolo[l,5-fl]pyrimidine 58 and its hydrated form were obtained by reaction of 5-amino-3-methylpyrazole with 2,6-bis(trifluoromethyl)-4-pyrone (57) [26]... 

Zarea et al. [126] reported an efficient multicomponent reaction for the synthesis of fused 6-amino-3-methyl-4-aryl-lH-pyrazolo[3,4-b]pyridine-5-carbonitrile (185) from substituted aldehydes (182), malononitrile (183), and 3-amino-5-methylpyrazole (184) (Scheme 48). The reaction has been carried out in the absence of catalyst and with the assistance of ultrasoxmd irradiation. Reported yields were good to excellent (85-98%) in short reaction times (8-10 min). 

---