Experimental and Theoretical Investigations of the Stereoselective Synthesis of P-Stereogenic Phosphine Oxides

An efficient enantioselective strategy for the synthesis of variously substituted phosphine oxides has been developed, incorporating the use of (1S,2S)‐2‐aminocyclohexanol as the chiral auxiliary. The method relies on three key steps: 1) Highly diastereoselective formation of PV oxazaphospholidine, rationalized by a theoretical study; 2) highly diastereoselective ring‐opening of the oxazaphospholidine oxide with organometallic reagents that takes place with inversion of configuration at the P atom; 3) enantioselective synthesis of phosphine oxides by cleavage of the remaining PO bond. Interestingly, the use of a PIII phosphine precursor afforded a P‐epimer oxazaphospholidine. Hence, the two enantiomeric phosphine oxides can be synthesized starting from either a PV or a PIII phosphine precursor, which constitutes a clear advantage for the stereoselective synthesis of sterically hindered phosphine oxides. That's handy: An efficient enantioselective strategy for the synthesis of variously substituted phosphine oxides was developed, incorporating the use of (1S,2S)‐2‐aminocyclohexanol as a chiral auxiliary, whereby enantiomeric phosphine oxides can be synthesized starting from either a PV or a PIII phosphine precursor.