Electron-Poor Chiral Diphosphine Ligands: High Performance for Rh-Catalyzed Asymmetric 1,4-Addition of Arylboronic Acids at Room Temperature

Electron-poor chiral diphosphine ligands, MeO-F28-BIPHEP (1a) and MeO-F12-BIPHEP (1b), were synthesized for controlling a transition-metal catalyst electronically. The 1b-ligated Rh catalyst showed excellent catalytic activity with high % ee for asymmetric 1,4-addition of arylboronic acids to α,β-unsaturated carbonyls at 20 °C. The strong π-acceptor ability of 1b induces transmetalation of arylboronic acid to catalyst precursor [RhCl(1b)]2 directly in the first step of the catalytic cycle.