The trivalent phosphine-catalyzed [4+1] spiro-annulation reaction of allenyl imide and activated methylene cyclocompounds has been developed for the construction of various spiro-2-cyclopenten-1-ones. Oxindoles, 3-isochromanones, and 2-indanones are selected as 1C synthons to capture the in situ-generated bis-electrophilic α,β-unsaturated ketenyl phosphonium intermediate, affording the corresponding monospiro- and bispiro-cyclopentenones in good to excellent yields (≤91%) under mild conditions. The primary attempt at asymmetric catalysis using monophosphine (R)-SITCP provides promising enantioselectivity (45% ee). A plausible reaction mechanism is also proposed.

中文翻译：

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三价膦催化烯酰亚胺和亚甲基环化合物的 [4+1] 螺环化反应

联烯基酰亚胺和活化的亚甲基环化合物的三价膦催化的[4+1]螺环化反应已被开发用于构建各种螺-2-环戊烯-1-酮。选择羟吲哚、3-异色满酮和 2-茚满酮作为 1C 合成子，捕获原位生成的双亲电子 α,β-不饱和烯基鏻中间体，以良好至优异的产率提供相应的单螺环和双螺环戊烯酮（≤ 91%）在温和条件下。使用单膦 ( R )-SITCP进行不对称催化的初步尝试提供了有希望的对映选择性 (45% ee)。还提出了一种合理的反应机制。