Structural effects in the Pd-induced enantioselective deprotection–decarboxylation of β-ketoesters

Structural effects in the chiral base and the influence of some key reaction parameters (catalyst type and solvent) in the Pd-induced enantioselective decarboxylation (cascade reaction) of three different ,-disubstituted benzyl β-ketoesters were explored. The reaction intermediate after debenzylation (β-keto-carboxylic acid) was synthesized and its decarboxylation studied independently. The highest ee (up to 60%) in the cascade reaction was achieved with those substrates that contained an aromatic ring system and with chiral amino alcohols that possessed an extended aromatic ring (quinine and quinidine). Polar solvents with weak H-bond donor and acceptor properties favor enantioselection.