Asymmetric Synthesis of Fused Polycyclic Indazoles through Aminocatalyzed Aza-Michael Addition/Intramolecular Cyclization

The first example of an asymmetric aminocatalyzed aza-Michael addition of 1H-indazole derivatives to α,β-unsaturated aldehydes is described. The iminium/enamine cascade process lies at the heart of our strategy, leading to enantioenriched fused polycyclic indazole architectures. Variations on both the α,β-unsaturated aldehydes and the indazole-7-carbaldehyde heterocycles were studied in order to broaden the scope of the transformation in synthetically interesting directions. The fused polycyclic indazoles exhibit fluorescence properties and can undergo synthetic transformations.