Design of new reactions using N-Heterocyclic carbenes as organocatalysts

N-杂环卡宾(NHCs)由于其独特的性质引起了化学界的广泛关注。作为强大的电子给体，它们迅速成为一类重要的过渡金属配体。此外，在没有过渡金属的情况下，它们也可以作为催化剂。被NHCS加速的大多数反应的共同之处是醛的正常反应活性发生逆转。这些官能团通常以亲电性(电子受体)的形式反应，在催化过程中变成亲核性(电子供体)。尽管具有这种独特的反应活性可逆性，但NHCS直到最近才被应用于数量迅速增加的迄今未知的反应。我们在这方面的工作主要集中在新的扩环反应和由NHCS引发的多米诺骨牌反应的发展上。这项建议详细列出了我们在未来五年将追求的四个新方向。将根据反应性逆转的概念设计新的多米诺骨牌Diels-Alder和Stetter反应，并将开发更有效的催化剂。亲核催化，一种较少被探索的NHCS反应性模式也将被探索。这些进展将应用于生物活性天然产物及其类似物的合成。

Due to their unique properties, N-heterocyclic carbenes (NHCs) have attracted a lot of attention from the chemistry community. Being powerful electron donors, they have rapidly established themselves as an important class of ligands for transition metals. Moreover, they can also act as catalysts in the absence of transition metals. Common to most reactions that are accelerated by NHCs is the reversal of the normal reactivity of aldehydes. These functional groups, which usually react as electrophiles (electron-acceptors), become nucleophiles (electron-donors) in the catalyzed process. Despite this unique property of reactivity reversal, NHCs have only recently been applied to a rapidly increasing number of hitherto unknown reactions. Our own efforts in this area have focused on novel ring expansion reactions and on the development of domino reactions initiated by NHCs. This proposal details four new directions we will pursue over the next five years. New domino Diels-Alder and Stetter reactions will be designed based on the concept of reactivity reversal, and more efficient catalysts will be developed. Nucleophilic catalysis, a less-explored mode of reactivity for NHCs will also be explored. These advances will be applied to the synthesis of biologically active natural products and their analogues.