Asymmetric Synthesis of Novel Ferrocenyl Ligands with Planar and Central Chirality and Their Application to Pd-Catalyzed Allylic Substitutions

摘要

An efficient and flexible asymmetric synthesis of planar chiral ferrocenyl ligands bearing a stereogenic centre at the β-position to the metallocene backbone is described. A variety of donor groups can be independently introduced as electrophiles, thus allowing electronic and steric fine-tuning of the ligands, which were investigated in Pd-catalyzed enantioselective allylic substitutions. By employing a P,S ligand, the alkylation of the standard test system (±)-1,3-diphenyl-2-propenyl acetate using dimethyl malonate/BSA as the nucleophile proceeded in a quantitative yield with an ee of 97%, which is the best value reported so far in this reaction for a P ∪ S ligand.