Organocatalytic Enantioselective Higher‐Order Cycloadditions of In Situ Generated Amino Isobenzofulvenes

The [8+2] cycloaddition of indene‐2‐carbaldehydes and nitro olefins is described to provide benzonorbornene scaffolds in a highly peri‐, diastereo‐, and enantioselective fashion in the presence of a C2‐symmetric aminocatalyst. This reaction, which proceeds through a transient semi‐aromatic amino isobenzofulvene, represents the first example of catalytic formation and transformation of these species. Quantum chemical calculations suggest a kinetically controlled stepwise mechanism where the stereochemistry is determined in the first bond‐forming event. Beyond the useful [8+2] cycloadducts, [10+4] cycloadducts have been identified in silico as potential off‐pathway intermediates. After a fashion: Experimental and computational studies detail the catalytic formation and transformation of transient amino isobenzofulvenes by stereoselective [8+2] cycloaddition reactions with electron‐deficient olefins. Benzonorbornene scaffolds are obtained in a highly peri‐, diastereo‐, and enantioselective fashion in the presence of a C2‐symmetric aminocatalyst.