[189210-88-6] · C14H19P · (MW 217.97)
(chiral, nonracemic phosphine ligand for asymmetric transition metal-catalyzed reactions)
Solubility: soluble in common organic solvents (i.e., benzene, toluene, CH2Cl2).
Analysis of Reagent Purity: 1H-NMR.
Preparative Methods prepared in four steps starting from p-xylene.1 Birch reduction of p-xylene followed by asymmetic hydroboration-oxidation provides an optically pure diol. The diol is subsequently converted to the chiral phosphine by formation of the corresponding dimesylate and nucleophilic addition of Li2PPh.
Purification: purification was accomplished by chromatography of the corresponding borane complex. Decomplexation using HBF4·O(C2H5)2 afforded the pure phosphine.
Handling, Storage, and Precautions: sensitive to atmospheric oxidation. Should be stored and handled under an inert atmosphere.
Chiral phosphines have played a crucial role in the development of catalytic asymmetric reactions. In particular, the coordination of a resolved, chiral phosphine to a transition metal center has been exploited to produce highly enantioselective catalysts for a variety of catalytic processes.2 Although there are many chiral monodentate and bidentate chiral phosphines available, (1R,2S,4R,5S)-2,5-dimethyl-7-phenyl-7-phosphabicyclo[2.2.1]heptane provides the advantage of a rigidified ring system that reduces the conformational flexibility present in many other phosphine ligands.
Application of this ligand to the Pd-catalyzed allylic alkylation of 1,3-diphenyl-2-propenyl acetate with dimethyl malonate provides an alkylated product in > 99.5% enantiomeric excess (
This ligand has also been shown to be effective in the direct organocatalysis of asymmetric processes.4 For example, the phosphine-catalyzed [3 + 2] annulation reaction of ethyl 2,3-butadienoate and isobutyl acrylate produces two cyclopentene regioisomers (1 and 2) (
The Ohio State University, Columbus, OH, USA