Diastereo- and Enantioselective Synthesis of Hexa-1,5-diene-3,4-diamines by Cobalt-Catalyzed Asymmetric Double Allylic Amination.

A highly diastereo- and enantioselective synthesis of hexa-1,5-diene-3,4-diamines has been developed based on cobalt-catalyzed double allylic amination of hexa-1,5-diene-3,4-diyl dimethyl dicarbonate. Consecutive stereocenters can be built under an asymmetric double allylic substitution strategy. Acyclic hexa-1,5-diene-3,4-diamines and cyclic tetrahydroquinoxalines were synthesized in up to 96% yield, >20:1 dr, and normally 99% ee. Cobalt catalysts exhibit a uniquely high reactivity over rhodium and iridium by overcoming the coordinating inhibition of the diene structure of both substrates and products. The chiral hexa-1,5-diene-3,4-diamines were not only used as chiral ligands for Rh-catalyzed conjugated 1,4-addition but also transformed into chiral N-heterocyclic carbene precursors and other chiral products.