Synthesis of the Diphosphane Ligands

The investigation and development of the enantioselective catalytic hydrogenations of the allylic alcohols required the ready availability of a number of BIPHEP type diphosphanes for screening and optimization purposes as well the availability of the most interesting ligands, i.e., of (S)-MeOBIPHEP (S-29) and (S)-pTol-BI- 

PHEP-type ligands, since, through activation to the bis(phosphonic dichlorides) they react with a large variety of aryl, heteroaryl or alkyl Grignard reagents to provide the bis(phosphane oxides), which then are reduced to the diphosphanes (cf. [56] and literature cited therein). 

The bis(phosphane oxide) resolution route to (S)-MeOBIPHEP (S-29), the ligand for the geraniol hydrogenation, was successfully developed to a larger scale process (Fig. 11). In this process, phosphinoylation of 3-bromoanisole was realized 

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