Rhodium‐Catalyzed Enantioselective Radical Addition of CX₄ Reagents to Olefins

Abstract

We describe the synthetically useful enantioselective addition of Br-CX₃ (X=Cl or Br) to terminal olefins to introduce a trihalomethyl group and generate optically active secondary bromides. Computational and experimental evidence supports an asymmetric atom-transfer radical addition (ATRA) mechanism in which the stereodetermining step involves outer-sphere bromine abstraction from a [(bisphosphine)Rh^II BrCl] complex by a benzylic radical intermediate. This mechanism appears unprecedented in asymmetric catalysis.