Copper-Catalyzed Asymmetric 4+1 Cycloadditions of Enones with Diazo Compounds To Form Dihydrofurans

This report describes the use of a planar-chiral bipyridine ligand to achieve the first diastereo- and enantioselective copper-catalyzed 4+1 cycloadditions of enones with diazo compounds to produce highly substituted 2,3-dihydrofurans. The method is applied to a catalytic asymmetric synthesis of a deoxy-C-nucleoside.