Hydrazone-Initiated Carbene/Alkyne Cascades to Form Polycyclic Products: Ring-Fused Cyclopropenes as Mechanistic Intermediates

A hydrazone-based carbene/alkyne cascade produced a variety of bridged and fused polycyclic products. NaOSiMe3 is a superior base for conversion of hydrazones to diazoalkanes. A key mechanistic intermediate, a ring-fused cyclopropene, has been isolated and characterized.