N-Tosylhydrazones generated in situ from cyclicketones smoothly underwent a [3 + 2] cycloaddition to afford saturated spirocyclic pyrazoles and further transformed to the fused analogues via a ringexpansion in certain cases. An inexpensive and renewable resource, calcium carbide, was utilized as the carbon source in the ringexpansion. The salient features of this reaction include widely available
To date, [3 + 2] cycloadditions of diazo esters with alkynes or alkenes have been a robust tool to generate pyrazoles and pyrazolines. However, methods capable of generating donor/donor diazo species from readily available N-tosylhydrazones to furnish [3 + 2] cycloadditions, remain elusive. Herein, we describe the first visible-light-induced [3 + 2] cycloadditions of donor/donor diazo precursors with