Intermolecular [3+2] MIRC reactions with alkynoates. Asymmetric Michael addition leading to a nonracemic cyclopentene-annulated α,β-butenolide

A novel Michael-initiated ring closure reaction involving allylic chlorosulfone (2) and γ-alkoxy-α,β-ynoates to afford 4-methylenecyclopentenecarboxylates is reported, while with γ-alkylynoates no reaction occurred. With chiral phenyl ynoates 4, the reaction proceeds by 1,3-asymmetric induction and leads further to a nonracemic annulated α,β-butenolide (7).