NOVEL PERFLUOROALKYL-SUBSTITUTED PYRAZOLES .1. HYDROXYPYRAZOLES

Addition of methylhydrazine to a variety of haloalkyl-substituted alpha,beta-unsaturated esters gives 1,5-disubtituted 3-hydroxypyrazoles, in contrast to the more common synthesis from beta-ketoesters, which gives 1,3-disubstituted 5-hydroxypyrazoles. This reaction is used to prepare several novel pyrazoles bearing haloalkyl substituents. Criteria for assignment of structures have been developed based on physical and spectroscopic properties of the isomers. The regiochemical preference in this addition is considered on the basis of steric, electronic, and mechanistic factors.