Copper Carbenoid, Reactant and Catalyst for One-Pot Diazo Ester Coupling Cascade Rearrangement of Enediynes: Formation of Two Contiguous Tetrasubstituted Stereocenters
Abstract
The copper-catalyzed reaction of enediynes with diazo esters leads to cyclic amino esters bearing two contiguous tetrasubstituted stereogenic centers through a one-pot, five-step cascade. Copper iodide catalyzes the formation of an intermediate 3-alkynoate and copper carbenoid promotes its reversible isomerization to the corresponding allenoate. The alkynoate-allenoate equilibrium is completely shifted to the right by the rapid consumption of the allenoate by MyersSaito cyclization. This is followed by 1,5-H atom transfer and recombination of the resulting biradical. Memory of chirality phenomenon explains the high enantioselectivity.