| 12713309 |
Jiang XB, Minnaard AJ, Hessen B, Feringa BL, Duchateau AL, Andrien JG, Boogers JA, de Vries JG: Application of monodentate secondary phosphine oxides, a new class of chiral ligands, in Ir (i)-catalyzed asymmetric imine hydrogenation. Org Lett. 2003 May 1;5(9):1503-6.
Secondary phosphine oxides were prepared from R (1) PCl (2) and R (2) MgBr, followed by hydrolysis. They were obtained in an enantiopure form by preparative chiral HPLC. These new monodentate ligands were tested in the iridium-catalyzed hydrogenation of imines at 25 bar. Enantioselectivities up to 76% were obtained at L/Ir = 2. Addition of pyridine (Pyr/Ir = 1:2) raised the ee to 83%. Using pyridine as an additive allowed reduction of the L/Ir ratio to 1 without reduction of ee. [reaction: see text] |
6(0,0,1,1) |