Structural Revision in Pyrazole Chemistry

Reaction of several heteroarylhydrazines with β-diketones has been incorrectly reported to generate triazepines or diazepines.It has now been firmly established that these reactions lead to the formation of pyrazoles.Further, many workers have reported the formation of pyrazoles in the reaction of heteroarylhydrazines with trifluoromethyl 1,3-diketones, whereas the actual products were found to be 5-hydroxy-5-trifluoromethyl-4,5-dihydro-1H-pyrazoles.It was also established that with a trifluoromethyl β-diketone and hydrazines, the location of the CF 3 group at position 3 or 5 of pyrazoles depends on the nature of the hydrazine.Erroneous reports concerning the structure of the products obtained by the reaction of dehydroacetic acid with hydrazines have also been revised.