Haloacetylated enol ethers 10. Condensation of beta-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 reactio n of beta-alkoxyvinyl trifluoromethyl ketones (1a-g) with thiosemicarbazide in methanol, under mild conditions, is reported. Similarly, the 1H-1-pyraz olethiocarboxyamide derivatives (2a-g) were easily dehydrated and the thioc arboxyamide group hydrolyzed in a one-step reaction by stirring with concen trated sulfuric acid to give the 3-aryl[alkyl]-5-trifluoromethyl-1H-pyrazol es (3a-g) in good yields. Specific syntheses and physical properties of 3-a ryl [alkyl]-5-hydroxy-5-trifluoromethyl-4,5-dihydro-1H-1-pyrazolethio-carbo xyamides are reported here for the first time. (C) 1998 Elsevier Science S. A. All rights reserved.