Synthesis and cycloaddition chemistry of oxetanyl-substituted sydnones

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 by cross-coupling reactions.