Asymmetric Synthesis of Spirocyclic Oxindole δ‑Lactams via NHC-Catalyzed Formal [2+4] Annulation of Aliphatic Aldehydes with Oxindole-Derived α,β-Unsaturated Ketimines

An N-heterocyclic carbene (NHC)-catalyzed formal [2+4] annulation reaction of aliphatic aldehydes with oxindole-derived α,β-unsaturated ketimines under oxidative conditions is reported, affording spirocyclic oxindole δ-lactams with good yields, moderate diastereoselectivies, and good to excellent enantioselectivies. This reaction can be readily carried out on a gram scale, and the products could be further transformed to other synthetically useful compounds.本文报道了一种氮杂环卡宾（N-heterocyclic carbene, NHC）催化的、氧化条件下脂肪醛与靛红衍生α,β-不饱和酮亚胺的形式[2+4]环化反应，该反应可得到具有良好收率、中等非对映选择性以及良好至优异对映选择性的螺环靛红δ-内酰胺产物。该反应可便捷实现克级规模放大，且所得产物可进一步转化为其他具备合成应用价值的化合物。