A General and Regioselective Synthesis of 5-Trifluoromethyl-pyrazoles
作者:Robert S. Foster、Harald Jakobi、Joseph P. A. Harrity
DOI:10.1021/ol3021918
日期:2012.9.21
Two synthetic approaches to 4-trifluoromethylsydnones, a novel class of these mesoionic reagents, are reported. These compounds undergo regioselective alkyne cycloaddition reactions, thereby providing a generalapproach to 5-trifluoromethylpyrazoles. This method has been employed in a short formal synthesis of the herbicide fluazolate.
Oxetan-3-one reacts with 4-metallated sydnones to provide functionalised precursors to a variety of novel pyrazoles. Intermolecular cycloadditions were found to proceed in variable yield, but intramolecular cycloadditions were very efficient and provide an effective means to generate spiro-substituted heterocyclic intermediates. The potential of these compounds for further elaboration has been highlighted