A Versatile Enantioselective Catalytic Cyclopropanation-Rearrangement Approach to the Divergent Construction of Chiral Spiroaminals and Fused Bicyclic Acetals.

A highly enantioselective synthesis of various chiral heterobicyclic molecules including spiroaminals and fused bicyclic acetals has been developed via a chiral copper catalyzed cyclopropanation-rearrangement (CP-RA) approach under mild reaction conditions. Remarkably, the asymmetric CP-RA for exocyclic vinyl substrates without a pro-stereogenic carbon at the ß-position has been realized for the first time and a broad substrate scope with excellent results (33 examples; 34-99 % yields; >95/5 dr and 91-99 % ee) has been achieved. An application of a successive enantioselective CP-RA approach was also described, providing a concise access to complex chiral heteropolycycles.

One-Pot Catalytic Asymmetric Synthesis of Tetrahydrocarbazoles.

A one-pot asymmetric synthesis of 1,2,3,4-tetrahydrocarbazoles has been developed via an enantioselective [3 + 3] annulation of 2-alkynylindoles and donor-acceptor cyclopropanes. In the presence of chiral Lewis acids as catalysts, a series of optically active tetrahydrocarbazoles were furnished in high yields (63-87%) with good to excellent levels of enantioselectivity (up to 94% ee).