A Chiral Bis(arsine) Ligand: Synthesis and Applications in Palladium-Catalyzed Asymmetric Allylic Alkylations

The
new chiral bis­(arsine) ligand N,N′-bis­[2′-(diphenylarsino)­benzoyl]-(1R,2R)-cyclohexanediamine (BiAsBA, 3), based on the backbone of the Trost modular ligand
(TML), was synthesized in three steps. A useful approach to introduce
the −AsPh2 group on arsine ligands by Pd-catalyzed
arsination was used. The molecular structure and configuration of
the BiAsBA ligand was determined by single-crystal
X-ray crystallography. In the asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl
acetate with dimethyl malonate very high to complete conversion and
modest enantioselectivity were achieved. Despite the low enantioselectivity
obtained, the bis­(arsine) ligand BiAsBA showed significant
potential, since it provided a higher ee value than the phosphorus-containing
homologous “Trost standard ligand” (TSL) with the same
substrate.