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 beta,gamma-unsaturated alpha-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 stereosynergistic effects of the sidearm.