Síntese e reações de 5-trifluormetil- 4,5-diidro-1H-1-pirazoltiocarboxamida 3(4)-substituídos

Abstract

This thesis describes the synthesis and application as bi-heterocyclic precursor a series of 3-aryl[alkyl]-5-hydroxy-5-trifluoromethyl-4,5-dihydro-1H-1- pyrazolethiocarboxamides (2), which are easily obtained from the direct cyclocondensation reaction of β-alkoxyvinyl trifluoromethyl ketones (1) with thiosemicarbazide in methanol, under mild conditions (r.t - 450C, 20-24 h) and in good yields (73-96%). Similarly, the 1H-1-pyrazolethiocarboxamide derivatives (2) were dehydrated and the thiocarboxamide group hydrolyzed in an one-step reaction by stirring with concentrated sulfuric acid under reflux for 4 hours to give the 3-aryl[alkyl]-5- trifluoromethyl-1H-pyrazoles (3) in good yield (57-75%). In a subsequent application reaction of 3-aryl[alkyl]-5-hydroxy-5-trifluoromethyl- 4,5-dihydro-1H-1-pyrazolethiocarboxamides (2), the synthesis of alkyl[aryl]-substituted 5-hydroxy-5-trifluoromethyl-4,5-dihydro-1H-1-methylpyrazoles (4) in good yields (68- 90%) from a new ring transformation reaction of alkyl[aryl]-substituted-5-hydroxy-5- trifluoromethyl-4,5-dihydro-1H-1-pyrazolethiocarboxyamides (2) with methylhydrazine in THF (2-7 hours a 20-250C), is reported. The thermal dehydration reaction of these pyrazolines (4) furnished the respective N-methylpyrazoles (5). Finally, a convenient method for the synthesis of a novel series of eighteen noncondensed 5,5-bicycles, specifically 2-(3-alkyl(phenyl)-5-hydroxy-5-trifluoromethyl-4,5- dihydro-1H-pyrazol-1-yl)-4-phenyl-5-alkyl-thiazoles and -4,5,6,7- tetrahydrobenzothiazoles (6), in good yields (57-98%), from the reaction of 3-alkyl(phenyl)-5-hydroxy-5-trifluoromethyl-4,5-dihydro-1H-1-pyrazolethiocarboxamide (2) with 2-bromoacetophenone, 2-bromopropiophenone and 2-bromocyclohexanone, is reported. The dehydration of these compounds by stirring at reflux for 5 hours with a mixture of concentrated sulfuric acid/acetic acid 1:10 v/v, led to the corresponding 2-[3- alky(phenyl)-5-trifluoromethyl-1H-pyrazol-1-yl]-4-phenyl-5-alkylthiazoles and respective -4,5,6,7-tetrahydrobenzothiazoles (7) in good yield (75-93%).