《表S2化合物5g晶体结构数据》

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《"基于α-溴代酮的催化不对称合成3,3-螺环丙基吲哚酮和乙烯基环丙烷（英文）"》

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Given the biological importance of 3，3-spirocyclopropyl oxindoles，[13]synthesis of chiral spirocyclopropyl oxindoles has been intensively investigated，particularly in the recent decade，and a series of metal-mediated and organocatalytic asymmetric cyclopropanations have been accordingly developed from specific oxindole derivatives，providing facile assemblies of such chiral molecular motifs.[5c～6f，6a～6h，7a～7c]Considering the easy availability of cinchona alkaloids and their derivatives as chiral catalysts，and the robustness of the Gaunt protocol in synthesis of chiral cyclopropanes，we were interested in exploring new synthesis of chiral 3，3-spirocyclopropyl oxindoles via catalytic ammonium ylide-mediated asymmetric cyclopropanation of 3-（substituted methylene）oxindoles.To test the feasibility of the suspected reaction，the racemic cyclopropanation between（E）-1-benzyl-3-（benzoylmethylene）oxindole（2a）and a quaternary ammonium salt prepared fromα-bromoacetophenone（1a）and 1，4-diazabicyclo[2.2.2]-octane（DABCO）was first examined.Thus，the ammonium salt（0.15 mmol）was treated with 2a（0.10 mmol）and Na2CO3（0.15 mmol）in 1，4-dioxane with stirring at 90℃for 3 h，delivering the expected spirocyclopropyl oxindole rac-3a in 70%isolated yield with>20∶1 dr diastereoselectivity（Eq.1）.