Cu-Catalyzed Diastereo-\nand Enantioselective Synthesis\nof Homopropargyl Amines Bearing All-Carbon Quaternary Stereocenters\nvia Chirality Transfer of Hindered Allenylcopper Species

The construction of congested acyclic stereocenters with\nhigh stereoselectivity\nis a significant challenge in synthetic chemistry. Herein, we report\nan efficient method for diastereo- and enantioselective C–C\ncoupling of 1,3-disubstituted enynes with imines for the asymmetric\nconstruction of vicinal stereogenic centers, including an all-carbon\nquaternary center. This coupling was accomplished by chirality transfer\nfrom axial-to-central of fully substituted axially chiral allenylcopper\nintermediates formed in situ from branched enynes with concomitant\ndiastereoselective formation of an additional stereocenter in imine\naddition enabled by a chiral C<sub>1</sub>-symmetric <i>N</i>-heterocyclic carbene (NHC) copper catalyst. DFT calculations provided\nan enhanced understanding of the silyl effect of allenylcopper nucleophiles\non reactivity and the origin of stereoselectivity. Synthetic versatility\nof the resulting products bearing densely functionalized groups could\namplify the significance of the current method.