Hydrogen-Bond-Promoted Palladium Catalysis: Allylic Alkylation of Indoles with Unsymmetrical 1,3-Disubstituted Allyl Acetates Using Chiral Bis(sulfoxide) Phosphine Ligands

摘要

The palladium-catalyzed asymmetric allylic alkylation (AAA, Tsuji-Trost reaction) is a powerful strategy for construction of carbon-carbon (C—C) and carbon-heteroatom (C—X) bonds.Various ligands, such as monodentate phosphines, bidentate N,N-, P,N-, P,P-ligands, etc., have been used in this reaction, especially for symmetric 1,3-disubstituted allylic substrates.8 To date, asymmetric alkylation (C—C bond formation) of racemic, unsymmetric 1,3-disubstituted substrates have been rarely reported, and a kinetic resolution is the only approach for providing the AAA products with a maximum of yield of 50 % [Eq. (1) and (2); see Figure 1 for catalyst structures; FcP = (R)-N-methyl-N-bis(hydroxyl-methyl)methyl-1-[(S)-1',2-bis(diphenyl)phosphine]ferrocenyl- ethylamine; TMS = trimethylsilyl] . However, the dynamic kinetic asymmetric transformation (DYKAT), as a straightforward method to transform racemic starting materials to optically pure products with a potential 100% yield, still remains a challenge.