Atropisomerism at the carbon–phosphorus bond

The feasibility of halting the rotation about a C–P bond is reported. At the outset, atropisomers with configurationally stable stereogenic C–P axes were synthesized in the form of triptycyl phosphine oxides with threefold stereogenicity. Their bond rotational profile revealed that each of the three barriers amounts to more than 115 kJ/mol, which permits the isolation of the antiperiplanar and the two enantiomeric synclinal C–P atropisomers under ambient conditions. Furthermore, the feasibility of their atroposelective synthesis by desymmetrization was established to catalytically control the configuration of stereogenic C–P axes. A first application of the synthesized C–P atropisomers was demonstrated by determining the absolute configuration of a protected amino acid.