Asymmetric Synthesis of <i>P</i>‑Stereogenic Compounds via Thulium(III)-Catalyzed Desymmetrization of Dialkynylphosphine Oxides

A chiral thulium­(III)-catalyzed sulfur-conjugation addition reaction of dialkynylphosphine oxides to construct P-stereogenic centers has been developed. Dialkynylphosphine oxides bearing aryl, alkyl, alkenyl substitution at the alkyne terminus position were tolerated under the reaction conditions. The corresponding P,S-containing compounds were obtained in moderate to good yields (up to 92% yield) with high Z/E ratios and enantioselectivities (up to >95/5 Z/E and 97% ee), which could be transformed into versatile optically active phosphine oxide derivatives. X-ray single crystal structures of chiral N,N′-dioxides with rare-earth metal triflates revealed how the metal center and ligand structure affect the enantioselectivity.