Paul Mathias, Sudkaow Panyapon, Wessels Alina, Schlörer Nils E, Neudörfl Jörg-M, Berkessel Albrecht
Cologne University, Department of Chemistry, Organic Chemistry, Greinstrasse 4, 50939, Cologne, Germany.
Angew Chem Int Ed Engl. 2018 Jul 2;57(27):8310-8315. doi: 10.1002/anie.201801676. Epub 2018 Jun 7.
We report the first generation and characterization of elusive Breslow intermediates derived from aromatic N-heterocyclic carbenes (NHCs), namely benzimidazolin-2-ylidenes (NMR, X-ray analysis) and thiazolin-2-ylidenes (NMR). In the former case, the diamino enols were generated by reaction of the free N,N-bis(2,6-diisopropylphenyl)- and N,N-bis(mesityl)-substituted benzimidazolin-2-ylidenes with aldehydes while the dimer of 3,4,5-trimethylthiazolin-2-ylidene served as the starting material in the latter case. The unambiguous NMR identification of the first thiazolin-2-ylidene-based Breslow intermediate rests on double C labeling of both the NHC and the aldehyde component. The acyl anion reactivity was confirmed by benzoin formation with excess aldehyde.
我们报道了源自芳香族氮杂环卡宾（NHCs）的难以捉摸的布雷斯洛中间体的第一代合成及表征，即苯并咪唑啉 - 2 - 亚基（核磁共振、X射线分析）和噻唑啉 - 2 - 亚基（核磁共振）。在前一种情况下，游离的N，N - 双（2,6 - 二异丙基苯基） - 和N，N - 双（均三甲苯基） - 取代的苯并咪唑啉 - 2 - 亚基与醛反应生成二氨基烯醇，而在后一种情况下，3,4,5 - 三甲基噻唑啉 - 2 - 亚基的二聚体用作起始原料。首个基于噻唑啉 - 2 - 亚基的布雷斯洛中间体的确切核磁共振鉴定依赖于对NHC和醛组分的双重碳标记。通过与过量醛形成安息香证实了酰基阴离子的反应活性。
