A rational pre-catalyst design for bis-phosphine mono-oxide palladium catalyzed reactions

Significant catalyst loading reduction and increased reaction robustness have been achieved for a Pd-catalyzed asymmetric intramolecular C-N coupling through comprehensive mechanistic studies. Detailed kinetic, spectroscopic, and crystallographic analyses revealed that the mono-oxidation of the bis-phosphine ligand is critical for a successful transformation. P-31 NMR studies provided an understanding of the inefficient activation of the Pd(OAc)(2)/(R,R)-QuinoxP* pre-catalyst to form the active bis-phosphine mono-oxide-Pd(0) catalyst with competitive formation of a less active (R, R)-QuinoxP*PdBr2 complex. Based on these detailed mechanistic studies, a new series of bis-phosphine mono-oxides (BPMO)-ligated Pd(II) pre-catalysts have been rationally developed that allow for reliable and complete catalyst activation which should have general utility in academic and industrial settings.