Reactions of beta-methoxyvinyl trifluoromethyl ketones with 2-pyridinecarboxamidrazone A convenient route to trifluoromethylated 4,5-dihydro-1 H-1-picolinoylpyrazole hydrochlorides

摘要

A new series of six 3-aryl-5-hydroxy-5-trifluoromethyl-4,5-dihydro-1 H-1-picolinoylpyrazole hydrochlorides were synthesized in one-step in high yields by the reaction of beta-methoxyvinyl trifluoromethyl ketones with 2-pyridinecarboxamidrazone in the presence of hydrochloric acid. The hydrochloride salts were easily converted to the respective new series of free trifluoromethylated 4,5-dihydro-1H-1-picolinoylpyrazoles using triethylamine in anhydrous diethyl ether. X-ray structure and ~35Cl NMR data from the pyrazole hydrochlorides are reported.