A convenient synthesis of 3- and 5-amino-1H-pyrazoles via 3(5)-amino-4-(ethylsulfinyl)-1H-pyrazole desulfinylation
Résumé
Syntheses of 5-amino-3-aryl- and 3-amino-5-aryl-1H-pyrazoles from β-bromo-α-(ethylsulfanyl)cinnamonitrile are described. The β-bromo-α-(ethylsulfanyl)cinnamonitriles were oxidized with H2O2 to the corresponding β-bromo-α-(ethylsulfinyl)cinnamonitriles. Subsequent treatment of the resulting sulfoxides with hydrazine hydrate or methylhydrazine followed by hydrochloric acid hydrolysis afforded 5-amino-3-aryl- and 3-amino-5-aryl-1H-pyrazoles, respectively, in good yields.