Rhodium-Catalyzed Regio- and Enantioselective Allylic Amination of Racemic 1,2-Disubstituted Allylic Phosphates

Alkynylphosphines are rarely used as ligands in asymmetric metal catalysis. We synthesized a series of chiral bis(oxazoline)alkynylphosphine ligands and used them in Rh-catalyzed highly regio- and enantioselective allylic amination reactions of 1,2-disubstituted allylic phosphates. Chiral 1,2-disubstituted allylic amines were synthesized in up to 95% yield with >20:1 branched/linear (b/l) ratio and 99% ee from racemic 1,2-disubstituted allylic precursors. The sterically smaller linear alkynyl group on the P atom in the bis(oxazoline)alkynylphosphine ligands was the key to fit the new requirements of the introduction of bulky 2-R' groups.

Automated summary

In this study, alkynylphosphines were utilized as ligands in asymmetric metal catalysis for highly regio- and enantioselective allylic amination reactions. Chiral bis(oxazoline)alkynylphosphine ligands were synthesized and successfully employed in Rh-catalyzed reactions to produce chiral 1,2-disubstituted allylic amines with high yields and excellent enantioselectivity. The presence of a smaller linear alkynyl group on the phosphorus atom in the ligands played a crucial role in accommodating bulky 2-R' groups.