Predicting the origin of selectivity in NHC-catalyzed ring opening of formylcyclopropane: a theoretical investigation,Catalysis Science & Technology

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Predicting the origin of selectivity in NHC-catalyzed ring opening of formylcyclopropane: a theoretical investigation
Catalysis Science & Technology ( IF 4.4 ) Pub Date : 2020-11-14 , DOI: 10.1039/d0cy01768j
Yang Wang _{1,

2,

3,

4} , Yan Qiao _{3,

4,

5,

6,

7} , Yu Lan _{3,

4,

7,

8} , Donghui Wei _{3,

4,

7,

8}

Affiliation

Using density functional theory, we investigated the origin of selectivity in the N-heterocyclic carbene (NHC)-catalyzed transformation of formylcyclopropane with an alkylidene oxindole. Our proposed mechanism includes the formation of a Breslow intermediate, ring opening of cyclopropane, formation of an enolate intermediate, formal [4 + 2] cycloaddition and disassociation of the catalyst. The transformation from an enolate intermediate into an alkylidene oxindole determines the chemoselectivity and stereoselectivity. Local reactivity analysis indicates that the chemoselectivity in the controlled transition state of the [4 + 2] cycloaddition is intrinsically favored by the higher reactivity of the C [double bond, length as m-dash]

C moiety of the alkylidene oxindole. Electron localization function analysis indicates that the NHC alleviates the electronic density between Cα and Cγ, and thus facilitates opening of the cyclopropane ring. This knowledge of NHC organocatalysis helps predict the chemoselectivity of divergent reactions involving cyclopropane rings.

中文翻译：

预测NHC催化的甲酰基环丙烷开环中的选择性起源：理论研究

使用密度泛函理论，我们调查了N-杂环卡宾（NHC）催化的亚烷基吲哚甲酰基环丙烷转化的选择性起源。我们提出的机理包括Breslow中间体的形成，环丙烷的开环，烯醇中间体的形成，正式的[4 + 2]环加成和催化剂的离解。从烯醇化物中间体到亚烷基吲哚的转化决定了化学选择性和立体选择性。局部反应性分析表明，在[4 + 2]环加成的受控过渡态中，化学选择性固有地受到C较高反应性的促进 [双键，长度为m-破折号]