Asymmetric Synthesis of γ‑Lactones through Koga Amine-Controlled Addition of Enediolates to α,β-Unsaturated Sulfoxonium Salts

A chiral Koga amine-controlled asymmetric
synthesis of cis-γ-lactones through a formal
[3 + 2] cycloaddition
of enediolates with α,β-unsaturated sulfoxonium salts
is described. The desired structural motif was formed in moderate
to good yields (50–71% for 13 examples), with good to very
good diastereoselectivity (dr 5:1 to 10:1 for 20 examples), favoring
the cis-isomer, and good to excellent enantioselectivity
(70–91% ee for 13 examples).