Enantioselective Synthesis of Fused Polycyclic Tropanes via Dearomative [3+2] Cycloaddition Reactions of 2-Nitrobenzofurans

A straight synthetic approach to fused polycyclic tropane scaffold formation through an asymmetric dearomatization cycloaddition process of 2-nitrobenzofurans with cyclic azomethine ylides was successfully developed. In the presence of a chiral copper complex, derived from Cu(OAc)(2) and a diphosphine ligand, a series of fused polycyclic tropane derivatives were obtained in high yields (75-91%) with excellent enantioselectivities (90-98%). The utility of this method was showcased by the facile transformation of product.