Insights into Lewis base-catalyzed chemoselective [3 + 2] and [3 + 4] annulation reactions of MBH carbonates,Organic Chemistry Frontiers

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Insights into Lewis base-catalyzed chemoselective [3 + 2] and [3 + 4] annulation reactions of MBH carbonates
Organic Chemistry Frontiers ( IF 4.6 ) Pub Date : 2020-06-04 , DOI: 10.1039/d0qo00457j
Qianqian Deng _{1,

2,

3,

4,

5} , Shi-Jun Li _{1,

2,

3,

4,

5} , Donghui Wei _{1,

2,

3,

4,

5} , Yu Lan _{1,

2,

3,

4,

5}

Affiliation

Predicting the chemoselectivity of Lewis base-catalyzed annulations of Morita–Baylis–Hillman (MBH) carbonates is one of the most challenging questions in the organocatalysis field. The origin of chemoselectivity in Lewis base-catalyzed [3 + 4] and [3 + 2] annulations of MBH carbonates was theoretically explored in this work. The calculated results indicate that the general reaction pathway contains five steps: (1) nucleophilic addition on the α-carbon of MBH carbonates by a Lewis base, (2) dissociation of BocO⁻, (3) deprotonation of the α-carbon, (4) Michael addition, and (5) ring closure coupled with the dissociation of the Lewis base. The ring-closure step determines the chemoselectivity for the possible [3 + 4] and [3 + 2] annulation reactions. The chemoselectivity can be well predicted using frontier molecular orbital (FMO) analyses, which demonstrate that the different overlap modes of FMOs involved in ring-closure transition states control the chemoselectivity.

中文翻译：

刘易斯碱催化MBH碳酸盐的化学选择性[3 + 2]和[3 + 4]环化反应的见解

预测刘易斯碱催化的森田-贝利斯-希尔曼（MBH）碳酸盐的化学选择性是有机催化领域最具挑战性的问题之一。在这项工作中，从理论上探讨了路易斯碱催化的MBH碳酸酯的[3 + 4]和[3 + 2]环中的化学选择性的起源。计算结果表明，一般的反应途径包含五个步骤：（1）在MBH碳酸酯的α碳的亲核加成由路易斯碱，（2）BOCO的解离^-，（3）α-碳的去质子化，（4）迈克尔加成，和（5）闭环与路易斯碱的解离相结合。闭环步骤确定了可能的[3 + 4]和[3 + 2]环化反应的化学选择性。使用前沿分子轨道（FMO）分析可以很好地预测化学选择性，这表明参与闭环过渡态的FMO的不同重叠模式控制着化学选择性。

更新日期：2020-07-14

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