Development of a novel phosphoramidite-selenide ligand for Pd-catalyzed asymmetric allylic substitution

Application of sSPhos as a Chiral Ligand for Palladium-Catalyzed Asymmetric Allylic Alkylation

Palladium-catalyzed asymmetric allylic alkylation is a versatile method for C-C bond formation. Many established classes of chiral ligands can perform allylic alkylation reactions enantioselectively, but identification of new ligand classes remains important for future development of the field. We demonstrate that enantiopure sSPhos, a bifunctional chiral monophosphine ligand, when used as its tetrabutyl ammonium salt, is a highly effective ligand for a benchmark Pd-catalyzed allylic alkylation reaction. We explore the scope and limitations and perform experiments to probe the origin of selectivity. In contrast with reactions previously explored using enantiopure sSPhos, it appears that steric bulk around the sulfonate group is responsible for the high enantioselectivity in this case, rather than attractive noncovalent interactions.

Axially chiral N-alkyl-N-cinnamoyl amide type P,olefin ligands for Pd-catalyzed reactions

We synthesized N-alkyl-N-cinnamoyl amide type phosphine-olefin compounds 1 and found axial chirality in a C(aryl)-N(amide) bond in compounds 1 by HPLC analysis using a chiral stationary phase column. We successfully obtained enantiomeric isomers of 1 and demonstrated the use of (-)-1 for chiral ligands in Pd-catalyzed asymmetric allylic substitution reactions of allylic esters with indoles (up to 97% ee).