New Chiral Br??nsted Acids for Asymmetric Synthesis

描述（由申请人提供）：拱形联芳基配体VANOL和VAPOL形成具有硼氧烷核心的独特聚硼酸根阴离子，并且开始被认为是用于不对称催化的非常独特和通用的平台。作为质子化亚胺的离子对，该手性阴离子可实现亚胺与重氮化合物的氮丙啶化反应，具有很高的产率、非对映选择性和对映选择性。将进行包括天然丰度动力学同位素研究在内的机理研究，以了解硼氧烷催化剂是如何形成的，以及它在包括氮丙啶化反应在内的各种反应中是如何起作用的。环硼氧烷酸盐核心是阴离子的，并且具有七个氧，它们都带有一些负电荷，并且它可能充当模板，其中多于一种底物可以同时与环硼氧烷酸盐核心形成氢键，这有助于确定过渡态。计算将被说服，以努力了解如何基板相互作用的硼氧烷核心的过渡态的氮杂环丙烷化和其他反应。除了这种硼氧烷酸盐催化剂的独特结构之外，它的实用性由于以下事实而大大增强：它可以由配体、硼源、两当量的醇或酚和三当量的水通过底物组装。因此，通过该方法可以产生的催化剂的多样性几乎是无限的。还将进行调查，以确定该boroxinate催化剂在其他反应中的有效性，包括Darkite反应，[3+2]环加成，醛的氨基烯丙基化和Ugi反应。

DESCRIPTION (provided by applicant): The vaulted biaryl ligands VANOL and VAPOL form a unique polyborate anion with a boroxinate core and is beginning to be recognized as a very unique and versatile platform for asymmetric catalysis. As an ion-pair with a protonated imine, this chiral anion will effect the aziridination of imines with diazo compounds with very high yields, diastereoselectivity and enanatioselectivity. Mechanistic investigations including natural abundance kinetic isotope studies will be undertaken to understand how the boroxinate catalyst is formed and how it functions in a variety of reactions including aziridination reactions. The boroxinate core is anionic and has seven oxygens which all bear some of the negative charge and it is possible that it serves as a template in which more than one substrate can H-bond with the boroxinate core at the same time and this helps to determine the transition state. Computations will be persued in an effort to understand how the substrates interact with the boroxinate core in the transition state of the aziridination and other reactions. In addition to the unique structure of this boroxinate catalyst, its utility is greatly enhanced by the fact that it can be assembled by the substrate from the ligand, a boron source, two equivalents of an alcohol or phenol and three equivalents of water. The diverse array of catalysts that can be generated by this process is thus virtually limitless. Investigations will also be carried out to determine the effectiveness of this boroxinate catalyst in other reactions including the Darzens reaction, [3+2] cycloadditions, aminoallylation of aldehydes, and the Ugi reaction.