A chiral diphosphine containing hemilabile ether donor groups and its use in rhodium asymmetric hydroboration of styrene

The new homochiral diphosphine (R,R) -o-C6H4[CH2OCH2CH(Me)PPh 2]2 (1) was prepared from ethyl lactate in five steps. Because of the two hemilabile ether groups, the ligand can be visualized as a diphosphine containing two intramolecular solvent molecules. The cationic Rh(I) complex [Rh(1)](BF4) was prepared and used as the catalyst in the asymmetric hydroboration of styrene with catecholborane. The catalytic system is chemo- and regioselective, but it yields low enantiomeric excess. ©1999 Elsevier Science S.A. All rights reserved.