Cu(I)/Chiral Bisoxazoline-Catalyzed Enantioselective Sommelet–Hauser Rearrangement of Sulfonium Ylides

Catalytic asymmetric
thia-Sommelet–Hauser rearrangement
of sulfonium ylides remains a great challenge due to its multistep
reaction mechanism involving metal carbene formation, proton transfer,
and [2,3]-sigmatropic rearrangement. In particular, the key problem
of such reactions is the differentiation of the enantiotopic lone
pair electrons of sulfur, which generates the sulfonium ylide intermediate
bearing chirality on the sulfur atom. With a modified chiral bisoxazoline
ligand, we developed a Cu­(I)-catalyzed asymmetric thia-Sommelet–Hauser
rearrangement with good to excellent enantioselectivities. Mechanistic
studies provide insights into the details of the reaction mechanism.