Mixed Alkyl/Aryl Diphos Ligands for Iron‐Catalyzed Negishi and Kumada Cross Coupling Towards the Synthesis of Diarylmethane
Xufeng Ma, Han Wang, Yao Liu, Xing Zhao, Jun Zhang
Abstract
Abstract Mixed alkyl/aryl diphos ligands have been prepared and their application in iron‐catalyzed cross coupling of benzylic chlorides with diaryl zinc (Negishi) or aryl Grignard reagents (Kumada) towards the synthesis of diarylmethane has been evaluated. The iron−diphos catalytic system exhibited the enhanced activity and selectivity in the two coupling reactions. The electron‐rich mixed PPh 2 /PCy 2 ligands outperformed their symmetrical PPh 2 congeners, and led to decreased homocoupling byproduct formation. It indicates that the electronic effect of the ligands plays an important role in the catalytic performance. The Fe catalyst supported by L8 bearing an electron‐rich PCy 2 substituent and a sterically demanding tert‐butyl on ethene backbone exhibited the best catalytic performance and good functional group tolerance in the two cross coupling reactions.