From mesomeric betaines to anionic N-heterocyclic carbenes

内消旋甜菜碱是阴离子杂环卡宾的通用前体。然而，它们的合成潜力远未得到开发。通过去质子化，可以产生极富π电子的阴离子N-杂环卡宾，其也可以在卡宾碳原子上具有高π电子密度（取决于共辄的类型）。在对sydnones和münchnones进行了初步研究之后，本项目涉及四种额外的内消旋甜菜碱作为N-杂环卡宾的前体，它们的π-结构不同。它们是通过它们的CREF值来选择的，CREF值最近被引入来量化从合适的前体形成卡宾的容易程度。将讨论CREF值转化为化学及其与TEP和HEP值、1 JCSe耦合常数等的关系。将进行捕获反应（Se、S）、络合（Rh、Pd、Pt、Au、Ir、.）和催化活性的检查。令人惊讶的是，在酸中，悉尼酮-卡宾的二氧化碳加合物催化Suzuki-Miyaura反应。将研究这种交叉偶联对碱不稳定底物的应用，如氨基酸和二肽（容易与碱结合）和异恶唑以及苯并异唑（与碱发生快速环裂解）。

Mesomeric betaines are versatile precursors of anionic heterocyclic carbenes. However, their synthetic potential is far from being exploited. By deprotonation, extremly pi-electron-rich anionic N-heterocyclic carbenes can be generated which also - depending on the type of conjugation – can possess high pi-electron densities on the carbene carbon atom. After preliminary work on sydnones and münchnones, this project deals with four additional mesomeric betaines as precursors of N-heteroccylic carbenes, which differ in their pi-architectures. They have been chosen by their CREF values, which have been introduced recently to quantify the ease of carbene formation from suitable precursors. The translation of the CREF values into chemistry and their relationship to TEP and HEP values, 1JCSe coupling constants and others will be discussed. Trapping reactions (Se, S), complexations (Rh, Pd, Pt, Au, Ir, …), and examinations of the catalytic activities will be performed. Surprisingly, the carbon dixide adducts of sydnone-carbenes catalyze Suzuki-Miyaura reactions in acids. The application of this cross-coupling to base-labile substrates such as amino acids and dipeptides (which racemate easily with bases) and isoxazoles as well as benzisoazoles (which suffer from rapid ring-cleavages with bases) will be studied.