Formation of Diastereoisomerically Pure Oxazaphospholes and Their Reaction to Chiral Phosphane-Borane Adducts

Starting with achiral phosphines and (1S,2S)-2-(methylamino)-1-phenylpropan-1-ol ((+)-pseudoephedrine) or (1R,2S)-2-(methylamino)-1-phenylpropan-1-ol ((−)-ephedrine), as chiral auxiliaries, diastereoisomerically pure oxazaphospholes were prepared (Scheme 1). The configuration at the P-atom is controlled by the configuration at the Ph-substituted C(1) of (+)-pseudoephedrine or (−)-ephedrine, respectively. This was confirmed by X-ray crystal-structure analyses of two intermediate compounds in the synthesis route to the chiral triarylborane-phosphane adducts.