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.