A Simple Strategy for the Preparation ofP-Chirogenic Trost Ligands with Different Absolute Configurations

P-chirogenic compounds are useful ligands and organocatalysts in asymmetric synthesis. However, the lack of preparative methods and their configurational instability have significantly hampered their development. Herein, we report a simple strategy for the preparation of enantiomerically pureP,C-chirogenic diphosphines. Amidation of the borane adducts ofrac-phosphinobenzoic acids with enantiomerically puretrans-1,2-diaminocyclohexane afforded a 1:2:1 mixture of the diastereomers (C*,C*,R-p,R-p), (C*,C*,R-p,S-p), and (C*,C*,S-p,S-p), which were separated by column chromatography on silica gel. The prepared (C*,C*,R-p,R-p) and (C*,C*,S-p,S-p) stereoisomers were identical to those obtained from the enantiopure phosphines, which were synthesized by a multi-step route using chiral auxiliaries. Hence, this simple, short and convenient route towardsP,C-chirogenic diphosphines obviates the use of chiral auxiliaries and enables the access to diphosphines with differently configuredP-stereocenters.