Construction of Nitrogen Spirocycles in a Tandem Co(III)‐catalyzed C−H Activation/Dipolar Cycloaddition Reaction

Abstract Complex spirocyclic isoindolines and pyrrolidines are formed in a tandem process involving Co(III)‐catalyzed dienylation of cyclic C‐aryl nitrones with 2,3‐butadien‐1‐ol carbonates, followed by intramolecular 1,3‐dipolar cycloaddition. The nitrone moiety serves both as a directing group for the C(aryl)−H activation and the dipole in the cycloaddition step. High regioselectivity of the fused vs. bridged product can be obtained by adjusting the reaction temperature. Reactions with substituted allenic substrates provide heterocycles with additional stereocenters usually with complete diastereoselectivity. The reaction products were readily transformed further into other complex nitrogen‐containing spirocyclic systems.