Tunable Masks for Triggered N-heterocyclic Carbene Organocatalysis

在化学系化学结构、动力学和机理B （CSDM-B）项目的支持下，明尼苏达大学的Jessica Lamb正在研究一种通过催化控制化学反应活性的新方法。由于其广泛的用途，n -杂环碳烯（NHCs）是一类特别重要的催化剂，在过去的几十年里引起了人们的广泛关注。NHCs是敏感化合物，如果直接暴露于空气或湿气中就会降解；因此，小分子可以用来隐藏或“掩盖”NHC的反应性，直到用热或光在所需的时间释放NHC催化剂。尽管在这一领域进行了大量工作，但人们对改变小分子“掩膜”如何调整国家卫生健康委员会释放病毒的确切条件知之甚少。Lamb团队将探索新的掩膜结构，用于系统地研究掩膜的变化将如何改变NHCs的催化行为。这项工作对未来设计新的可释放催化剂、催化剂回收和聚合物合成具有广泛的意义。该项目位于催化，聚合物和物理有机化学的交叉点，因此将为支持的研究生和本科生提供优秀的跨学科培训和教育。兰姆小组由一群不同的科学家组成，他们积极参与外展活动，重点是招募和留住STEM（科学、技术、工程和数学）领域代表性不足的学者。潜在/可转换催化利用外部刺激来控制化学反应发生的时间和地点。n -杂环碳（NHCs）是一种强大的、可调节的有机催化剂，但它们对空气和水分的敏感性往往需要通过使用“隐蔽”NHCs来使用潜在催化。目前的掩膜NHC系统是有限的，因为加合物的键强度是由NHC的结构控制的，导致了催化剂的延迟和活性之间的权衡。该项目将研究通过改变掩膜而不是催化剂的结构来决定NHC加合键稳定性和释放的基本结构-性质关系。具体来说，Lamb小组将研究碳二亚胺和三芳基硼烷作为模块化掩膜支架，可以使用热或光作为外部刺激激活。这项工作将应用物理有机技术来理解和预测掩膜结构和加合物稳定性之间的结构-性质关系，然后进一步将稳定性与催化剂活性联系起来。这项工作将对本科生和研究生（包括来自代表性不足群体的学生）的教育产生社会影响，发表增加基础化学知识的研究，并通过支持Lamb博士的外展活动，专注于招募和留住代表性不足的化学学者。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With the support of the Chemical Structure, Dynamics, and Mechanisms B (CSDM-B) program in the Division of Chemistry, Jessica Lamb of the University of Minnesota is studying a new way to control chemical reactivity via catalysis. Because of their wide utility, N-heterocyclic carbenes (NHCs) are a particularly important class of catalysts that has garnered a lot of attention in the past few decades. NHCs are sensitive compounds that can degrade if exposed directly to air or moisture; therefore, small molecules can be used to hide, or “mask”, the NHC reactivity until heat or light is used to release the NHC catalyst at the desired time. Despite extensive work in this area, little is known about how changing the small molecule “mask” can tune the exact conditions under which the NHC will release. The Lamb group will explore new mask structures that will be used to systematically study how changes in the mask will alter the catalytic behavior of the NHCs. The work has broad implications for designing new releasable catalysts, catalyst recycling, and polymer synthesis in the future. The project lies at the intersection of catalysis, polymer, and physical organic chemistry and thus will provide excellent interdisciplinary training and education to the supported graduate and undergraduate students. The Lamb group is composed of a diverse group of scientists who are actively engaged in outreach activities focused on recruiting and retaining underrepresented scholars in the STEM (science, technology, engineering and mathematics) fields.Latent/switchable catalysis uses external stimuli to control when and where chemical reactions take place. N-Heterocyclic carbenes (NHCs) are powerful, tunable organocatalysts, but their sensitivity to air and moisture often necessitates the use of latent catalysis through the use of “masked” NHCs. Current masked NHC systems are limited because the adduct bond strength is controlled by the structure of the NHC, leading to a trade-off between latency and activity of the catalyst. This project will investigate fundamental structure-property relationships that dictate NHC adduct bond stability and release by changing the mask, not the catalyst, structure. Specifically, the Lamb group will investigate carbodiimides and triarylboranes as modular mask scaffolds that can be activated using heat or light as the external stimulus. This work will apply physical organic techniques to understand and predict structure-property relationships first between mask structure and adduct stability then further correlate that stability to catalyst activity. The work will have societal impact in terms of education of undergraduate and graduate students – including students from underrepresented groups – publication of research that increases fundamental chemical knowledge, and through supporting Dr. Lamb’s outreach activities focused on recruiting and retaining underrepresented scholars in chemistry.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.