Synthesis of a novel β-cyclodextrin-functionalized diphosphine ligand and its catalytic properties for asymmetric hydrogenation

The novel diphosphine ligand 6A,6B-bis(diphenylphosphino)-6A,6B-dideoxy-permetliylated-beta-cyclodextrin (6A,6B-PMCDP2) has been prepared by reacting 6A,6B-dimesyl-permetliylated-beta-cyclodextrin (or 6A,6B-bis(trifluoromethanesulfonyl)-permethylated-beta-cyclodextrin) with LiPPh2. A nine-bond P-P coupling of 10.2 Hz is observed for 6A,6B-PMCDP2. Treatment of 6A,6B-PMCDP2 with PtCl2(COD) and [Rh(COD)(2)]BF4 in dichloromethane produced PtCl2(6A,6B-PMCDP2) and [Rh(COD)(6A,6B-PMCDP2)]BF4, respectively. The rhodium complex [Rh(COD)(6A,6B-PMBCDP2)]BF4 is catalytically active for hydrogenation of alpha-acetamido-cinnamic acid, alpha-acetamidoacrylic acid, itaconic acid, and their methyl esters with optical yields up to 92% ee.