The first chemoselective tandem acylation of the Blaise reaction intermediate: a novel method for the synthesis of α-acyl-β-enamino esters, key intermediate for pyrazoles
A silver-catalyzed synthesis of 5-aryl-3-trifluoromethyl pyrazoles from reaction of various N'-benzylidene tolylsulfonohydrazides with ethyl 4,4,4-trifluoro-3-oxobutanoate is described. The reaction proceeds via sequential nucleophilic addition, intramolecular cyclization, elimination, and [1], [5]-H shift steps to afford the trifluoromethylated pyrazole products in moderate to excellent yields. The