Regiospecific synthesis of trichloromethyl substituted 4,5-dihydro-1H-1 -tosylpyrazoles

The regiospecific synthesis of a new series of eight 3-alkyl(aryl)-5-hydroxy-5-trichloromethyl-4,5-dihydro-1H-1-tosylpyrazoles is reported. The 1-p-tosyl-2-pyrazolines were obtained from the cyclocondensation reaction of 4-alkyl(aryl)-4-alkoxy-1,1,1-trichloroalk-3-en-2-ones, [where alkyl = H, Me and aryl = -C6H5, 4-CH3C6H4, 4-OCH3C6H4, 4-FC6H4, 4-ClC6H4, 4-BrC6H4,] with p-tosylhydrazine in 64 to 92 % yields, employing anhydrous toluene at reflux or diethyl ether at room temperature as the reaction condition.