Non-Condensed Trifluoromethylated 5,5-Bicycles: Synthesis of 2-[3-Alkyl(phenyl)-1H-pyrazol-1-yl]-4-phenyl-5-alkylthiazole and -4,5,6,7-tetrahydrobenzothiazole Systems

A convenient method for the synthesis of a novel series of eighteen non-condensed 5,5-bicycles, specifically 2-[3-alkyl(phenyl)-5-hydroxy-5-trifluoromethyl-4,5-dihydro-1H-pyrazol-1-yl]-4-phenyl-5-alkylthiazoles and -4,5,6,7-tetrahydrobenzothiazoles 3a-i from the reaction of 3-alkyl(phenyl)-5-hydroxy-5-trifluoromethyl-4,5-dihydro-1H-1-pyrazolethiocarboxyamide (1) with 2-bromoacetophenone, 2-bromopropiophenone and 2-bromocyclohexanone (2), is reported. The dehydration of compounds 3a-i 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 4a-i in good yield.