Asymmetric Iminium Ion Catalysis: An Efficient Enantioselective Synthesis of Pyranonaphthoquinones and β‐Lapachones

An addition–cyclization reaction cascade triggered by an organocatalyst was used for the enantioselective preparation of a series of biologically active 1,2- and 1,4-pyranonaphthoquinones from aliphatic and aromatic α,β-unsaturated aldehydes and 2-hydroxy-1-4-naphthoquinone. A trimethylsilyl-protected diarylprolinol serves as the Lewis base organocatalyst.