Haloacetylated enol ethers 10. Condensation of β-alkoxyvinyl trifluoromethyl ketones with thiosemicarbazide. Synthesis of new trifluoromethyl 4,5-dihydro-1 H-1-pyrazolethiocarboxyamides

Abstract

The synthesis of 3-aryl[alkyl]-5-hydroxy-5-trifluoromethyl-4,5-dihydro-1 H-1-pyrazolethiocarboxyamides ( 2a–g) from the direct cyclo-condensation reaction of β-alkoxyvinyl trifluoromethyl ketones ( 1a–g) with thiosemicarbazide in methanol, under mild conditions, is reported. Similarly, the 1 H-1-pyrazolethiocarboxyamide derivatives ( 2a–g) were easily dehydrated and the thiocarboxyamide group hydrolyzed in a one-step reaction by stirring with concentrated sulfuric acid to give the 3-aryl[alkyl]-5-trifluoromethyl-1 H-pyrazoles ( 3a–g) in good yields. Specific syntheses and physical properties of 3-aryl[alkyl]-5-hydroxy-5-trifluoromethyl-4,5-dihydro-1 H-1-pyrazolethiocarboxyamides are reported here for the first time.