Access to Allene‐Containing Molecules via Enantioselective Reactions of Azolium Cumulenolate Intermediates

Azolium cumulenolates are a special type of intermediates in N-heterocyclic carbene catalysis. They contain elongated linear structures with three contiguous C=C bonds and sterically unhindered α-carbon atoms. These structural features make it difficult to develop enantioselective reactions for these intermediates. Here we disclose the first carbene-catalyzed highly addition azolium cumulenolates. The reaction starts alkynals as precursors cumulenolate that undergo activated ketones. From same set substrates, both allene spirooxindole products can be obtained high yields excellent enantioselectivities. moieties our optically enriched carry rich reactivities transformed diverse molecules. scaffolds important motifs natural medicines.