Catalytic Enantioselective Hetero-[6+4] and -[6+2] Cycloadditions for the Construction of Condensed Polycyclic Pyrroles, Imidazoles, and Pyrazoles.

The development of the first chemo-, regio-, and stereoselective hetero-[6+4] and -[6+2] cycloadditions of heteroaromatic compounds via amino aza- and diazafulvenes is presented. Pyrroles, imidazoles, and pyrazoles substituted with a formyl group react with an aminocatalyst to generate an electron-rich hetero-6π-component that reacts in a chemo-, regio-, and stereoselective manner with electron-deficient dienes and olefins. For the hetero-[6+4] cycloaddition of the pyrrole system with dienes, a wide variation of both reaction partners is possible, providing attractive pyrrolo-azepine products in high yields and excellent enantioselectivities (99% ee).

Organocatalytic [10+4] cycloadditions for the synthesis of functionalised benzo[a]azulenes.

A direct and mild strategy for the synthesis of benzo[a]azulenes based on an organocatalytic [10+4] cycloaddition reaction is described. The strategy enables a diversity-oriented approach for the synthesis of various poly-functionalised azulenes from easily accessible starting materials.

Catalytic Enantioselective [10+4] Cycloadditions.

The first peri- and stereoselective [10+4] cycloaddition between catalytically generated amino isobenzofulvenes and electron-deficient dienes is described. The highly stereoselective catalytic [10+4] cycloaddition exhibits a broad scope with high yields, reflecting a robust higher-order cycloaddition. Experimental and computational investigations support a kinetic distribution of intermediate rotamers dictating the enantioselectivity, which relies heavily on additive effects.

Aminocatalyzed Synthesis of Enantioenriched Phenalene Skeletons through a Friedel-Crafts/Cyclization Strategy.

A series of enantioenriched phenalene-derived compounds were accessed by a Friedel-Crafts/cyclization strategy. Starting from α,β-unsaturated aldehydes and 2-naphthol derivatives, high levels of enantioselectivity were obtained through iminium-enamine catalysis. The catalytic system composed of a diphenylprolinol silyl ether organocatalyst and triethylamine as a base was applied to a combination of diversely functionalized substrates.

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.