Catalytic Asymmetric Synthesis of Tricyclic Carbon Frameworks

Significance

An organocatalytic asymmetric one-pot procedure for the construction of functionalized tricyclic carbon frameworks in good overall yields, high enantioselectivities and diastereoselectivities has been developed. Chiral α,α-diarylprolinol silyl ether 1 mediates a selective Michael reaction of linear aldehydes 2 to aromatic nitroolefins 3 (enamine catalysis) followed by a conjugate addition to α,α-unsaturated aldehydes 4 (iminium catalysis) as well as an intramolecular aldol condensation (enamine catalysis) to give cyclohexene derivates 5. Finally, an intramolecular Diels-Alder reaction in the presence of stoichiometric amounts of dimethylaluminum chloride completes the synthesis of decahydroacenaph­thylenes 6 and decahydrophenalenes 7. Five C-C bonds and eight stereocenters are generated in the four-step process.