Cy-SaBOX/Copper(II)-Catalyzed Highly Diastereo- and Enantioselective Synthesis of Bicyclic N,O Acetals

Facile and effective access for the asymmetric construction of the useful and important skeleton of the bicyclic N,O-acetals is described. Cu^II/SaBOX could catalyze the reaction of β,γ-unsaturated α-ketoesters with cyclic enamines efficiently, thus affording the desired products in excellent yields with excellent stereoselectivities (21 examples; up to 99 % yields; up to >95:5 d.r.; and 95–99 % ee). This reaction can be well performed on gram scale, even with only 1 mol % catalyst loading. The single-crystal structures of the copper complexes lead to a good understanding of the stereo-synergistic effects of the sidearm.