Regiospecific one-pot synthesis of new trifluoromethyl substituted heteroaryl pyrazolyl ketones

Abstract

A convenient and general method for the regiospecific synthesis of three novel series of 1-(2-thenoyl)-, 1-(2-furoyl)- and 1-(isonicotinoyl)-3-alkyl(aryl)-5-hydroxy-5-trifluoromethyl-4,5-dihydro-1H-pyrazoles, in good yields (53 – 91 %), from the cyclocondensation reactions of 1,1,1-trifluoro-4-alkoxy-4-alkyl(aryl)-but-3-en-2-ones, where alkyl = H and Me; aryl = -C6H5, 4-CH3C6H4, 4-CH3OC6H4, 4-FC6H4, 4-ClC6H4, 4-BrC6H4, 4-NO2CgH4 with 2-thiophenecarboxylic hydrazide, furoic hydrazide and isonicotinic acid hydrazide, respectively, is reported. Subsequently dehydration reaction of phenyl substituted 2-pyrazolines with P2O5 furnished the corresponding 1H-pyrazoles as mixture of regioisomers and in low yields (35 – 36 %).