Formation of Breslow Intermediates from N-Heterocyclic Carbenes and Aldehydes Involves Autocatalysis by the Breslow Intermediate, and a Hemiacetal,Angewandte Chemie International Edition

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Formation of Breslow Intermediates from N-Heterocyclic Carbenes and Aldehydes Involves Autocatalysis by the Breslow Intermediate, and a Hemiacetal
Angewandte Chemie International Edition ( IF 16.1 ) Pub Date : 2022-03-03 , DOI: 10.1002/anie.202117682
Alina Wessels ₁ , Martin Klussmann _{2,

3} , Martin Breugst ₁ , Nils E Schlörer ₁ , Albrecht Berkessel ₁

Affiliation

Under aprotic conditions, Breslow intermediates can be generated from N-heterocyclic carbenes such as imidazolidin-2-ylidenes ((hyphenation: “imidazol-idin-2-ylidenes”)) and aldehydes. But how is the intermediary “primary adduct” (PA) converted to the diaminoenol (BI)? Our kinetic study shows that the highly unfavorable 1,2-C-to-O H-shift is autocatalyzed ((hyphenation: “au-to-cata-lyzed”)) by the Breslow intermediate, and that a hemiacetal plays a crucial role in the presence of excess aldehyde.

中文翻译：

由 N-杂环卡宾和醛形成 Breslow 中间体涉及 Breslow 中间体和半缩醛的自催化

在非质子条件下，Breslow 中间体可以由 N-杂环卡宾生成，例如 imidazolidin-2-ylidenes（（连字符：“imidazol-idin-2-ylidenes”））和醛。但是中间的“初级加合物”（PA）是如何转化为二氨基烯醇（BI）的呢？我们的动力学研究表明，高度不利的 1,2-C-to-O H-shift 被 Breslow 中间体自动催化（（连字符：“自动催化”）），并且半缩醛起着至关重要的作用在过量醛的存在下。

更新日期：2022-03-03

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