Enantioselective Pd‐Catalyzed Allylic Substitution using Phosphite‐Oxazoline PHOX‐Based Ligands containing a Methylene Linker

Abstract

High enantioselectivities (up to 99 %) and activities (TOF's up to >4000 h−1) are accomplished in the Pd‐catalyzed allylic substitution of a wide range of substrate types and nucleophiles using a family of phosphite‐oxazoline ligands. These ligands were derived from the PHOX ligand by exchanging the phosphine moieties by biaryl phosphites and a methylene spacer was introduced between the oxazoline and the phenyl ring. The wide substrate scope is due to the ability of the ligand family to adapt their ligand parameters to the reacting substrate. This ability also explains its high performance in other type of catalytic processes.

The Evolution of Phosphite‐Oxazoline Ligands for the Pd‐Allylic Substitution and Their Application in Building Chiral Molecules

“…Another modification of the PHOX backbone was the introduction of a methylene spacer between the oxazoline and the phenyl ring to previous ligands L1 – L6 (new ligands L7 – L9c , g – h , Figure 4). [16] Positively, the ligands L7 – L9 were synthesized in just two steps using readily available starting materials.…”

Palladium‐ and Iridium‐Catalyzed Deracemization of Allylic Oxygen Compounds with Oxygen Nucleophiles

“…had described the palladium‐catalyzed reaction of the racemic allylic acetate rac ‐ 49 a with alcohols by using the ( S,S )‐configured oxazoline‐BINOL‐phosphite L 16 as ligand and detailed a study of the structure and reactivity of η 3 ‐allylpalladium complexes, containing L 16 as ligand (Scheme 24). [55a] The application of structurally related ligands for palladium had been described previously [55b,c] . The Pd⋅L 16 catalyzed reaction of rac ‐ 49 a with the corresponding benzyl alcohols proceeded with high enantioselectivities and gave the allylic ethers ent‐ 50 a , ent‐ 50 c and ent‐ 50 f in high yields.…”