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

The synthesis of 3-aryl[alkyl]-5-hydroxy-5-trifluoromethyl-4,5-dihydro-1H-1-pyrazolethiocarboxyamides (2a-g) from the direct cyclocondensation reaction of beta-alkoxyvinyl trifluoromethyl ketones (1a-g) with thiosemicarbazide in methanol, under mild conditions, is reported. Similarly, the 1H-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-1H-pyrazoles (3a-g) in good yields. Specific syntheses and physical properties of 3-aryl [alkyl]-5-hydroxy-5-trifluoromethyl-4,5-dihydro-1H-1-pyrazolethio-carboxyamides are reported here for the first time. (C) 1998 Elsevier Science S.A. All rights reserved.