Design and synthesis of a tridentate ligand inspired by the phenomenon of self-assembly catalysis and its application in the asymmetric alkynylation of N-(diphenylphosphinoyl) imines

Regiospecific Hydration of N-(Diphenylphosphinoyl)propargyl Amines: Synthesis of β-Amino Ketones by Au(III) Catalysis

A Au(III)-catalyzed regiospecific hydration of N-(diphenylphosphinoyl)propargyl amines has been developed to produce various β-amino ketones. These reactions are conducted in the presence of NaAuCl4·2H2O (10 mol %) in a mixed solvent of EtOH/H2O/CH2Cl2 (4:1:1) at room temperature to give the products in 45-71% yield. The high enantiomeric purity of a chiral N-(diphenylphosphinoyl)propargyl amine (85% ee) is maintained after hydration, which makes this method useful for the asymmetric synthesis of chiral β-amino ketones. Reduction of a β-amino ketone product with Zn(BH4)2 gives a 1,3-amino alcohol with modest diastereoselectivity.

Mechanistic Studies and Expansion of the Substrate Scope of Direct Enantioselective Alkynylation of α-Ketiminoesters Catalyzed by Adaptable (Phebox)Rhodium(III) Complexes

Mechanistic studies and expansion of the substrate scope of direct enantioselective alkynylation of α-ketiminoesters catalyzed by adaptable (phebox)rhodium(III) complexes are described. The mechanistic studies revealed that less acidic alkyne rather than more acidic acetic acid acted as a proton source in the catalytic cycle, and the generation of more active (acetato-κ(2)O,O')(alkynyl)(phebox)rhodium(III) complexes from the starting (diacetato)rhodium(III) complexes limited the overall reactivity of the reaction. These findings, as well as facile exchange of the alkynyl ligand on the (alkynyl)rhodium(III) complexes led us to use (acetato-κ(2)O,O')(trimethylsilylethynyl)(phebox)rhodium(III) complexes as a general precatalyst for various (alkynyl)rhodium(III) complexes. Use of the (trimethylsilylethynyl)rhodium(III) complexes as precatalysts enhanced the catalytic performance of the reactions with an α-ketiminoester derived from ethyl trifluoropyruvate at a catalyst loading as low as 0.5 mol % and expanded the substrate scope to unprecedented α-ketiminophosphonate and cyclic N-sulfonyl α-ketiminoesters.