Enantioselective Synthesis of Substituted δ‑Lactones by Cooperative Oxidative N‑Heterocyclic Carbene and Lewis Acid Catalysis

Efficient
construction of complex cylcopentane- or cyclohexane-fused
δ-lactones employing redox activation of enals using a chiral
N-heterocyclic carbene and LiCl as cooperative catalysts is described.
The organocascade proceeds with excellent diastereo- (>99:1) and
enantioselectivity
(up to >99% ee) and comprises the formation of three bonds with
three
contiguous stereocenters.

本研究报道了以手性氮杂环卡宾（chiral N-heterocyclic carbene）与氯化锂（LiCl）为协同催化剂，通过烯醛（enals）的氧化还原活化策略，高效构建环戊烷并/环己烷并δ-内酯类复杂分子的方法。该有机级联反应展现出优异的非对映选择性（>99:1）与对映选择性（最高可达>99%对映过量值（enantiomeric excess，ee）），且可同时生成三根化学键并构筑三个连续手性中心。