Synthesis of Asymmetric Diaryl Secondary Phosphines via P-C Cross-coupling

Abstract

Synthesis of asymmetric, diaryl, secondary phosphines with benzene backbone via Cu cross-catalysis was attempted from commercially available starting materials. Homogeneous and heterogenous reaction systems were used, with product conversion typically rising no higher than a 1:4 ratio compared to remaining starting material despite attempts to optimize reaction conditions by adjusting heating, base, supporting ligand, limiting reagent, and other relevant factors. The reaction was monitored by 31P NMR to determine the cause of inhibition. Evidence suggests early termination of catalysis due to the formation of inactive k2-bis(phosphide) complex. The process is generally chemically sound with the necessary steps as defined, but catalyst poisoning and product inhibition present serious obstacles for this synthesis