Application of SDP Ligands for Pd-Catalyzed Allylic Alkylation



Chiral spiro diphosphines (SDP) are efficient ligands for the Pd-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate with dimethyl malonate and related nucleophiles. The newly synthesized ligand DMM-SDP (1e) with 3,5-dimethyl-4-methoxy groups on the P-phenyl rings of the phosphine shows the highest enantioselectivity (up to 99.1% ee). Diethylzinc as a base is critical for obtaining high enantioselectivity in the allylic alkylation using β-dicarbonyl nucleophiles. The structure of catalyst [PdCl2((S)-SDP)] was determined by single crystal X-ray diffraction. The SDP ligands create an effective asymmetric environment around the palladium, resulting in high enantioselectivities for the asymmetric allylic alkylation reaction