Selective Catalysts with an Inward Facing N-Heterocyclic Carbene

化学催化计划支持纽约州立大学(SUNY)布法罗分校史蒂文·T·迪弗教授领导的合成新的大环N-杂环卡宾的研究。这种独特的大环设计具有一个多功能的配体，指向分子腔的内部。N-杂环卡宾是一种强大的亲核剂，既可用于催化碳-碳键的形成，也可用作过渡金属(如Ru)的配体。大环配体的设计目的是将过渡金属牢牢地固定在其内部，在那里发生选择性的烯烃歧化反应。目前的Ru卡宾催化剂表现出很高的化学选择性(优先选择烯烃)，但本研究解决了它们的一些关键缺点，包括分解、关键催化中间体的寿命和选择性。大环的限制性预计将限制分解途径，并将显示其化学反应物的大小选择性，这是烯烃歧化反应中一种未知类型的选择性。烯烃歧化反应是合成小分子、材料和能源的重要反应，广泛应用于大规模工业应用、药物合成和药物化学的药物发现。在国家科学基金化学部化学催化计划的支持下，Steven T.Diver教授和他的研究团队基于占据空穴内部的金属获得了具有广泛应用范围的新型化学催化剂。在这种受控环境下，研究了强亲核配体的基本性质。新型Ru卡宾催化剂的研究有望生产出更耐用的催化剂，用于可持续能源。例如，在生产经济可行的生物柴油燃料方面，寿命更长的Ru-Carbene催化剂至关重要。推广部分旨在通过一个面向高中生和K-12年级学生的催化项目，并依靠高中生和研究生领导活动，通过化学功勋徽章日，提高青年对化学作为一门实验科学的认识。动力学实验是演示如何通过实验控制自然现象以及如何呈现数据的理想工具。人们对具有更高活性、更长寿命和更高选择性的催化剂的需求很大，本研究项目中审查的烷烃歧化反应被用作制造化学生物学探针和染料的工具。Ru卡宾的包埋是通过限制双分子分解来控制催化剂选择性和提高催化剂稳定性的新途径。这一概念可能会被证明对其他金属催化应用具有广泛的实用价值。

The Chemical Catalysis Program supports research led by Professor Steven T. Diver at the State University of New York (SUNY) at Buffalo on the synthesis of a new macrocyclic N-heterocyclic carbene. This unique macrocycle design features a versatile ligand pointing inward toward the inside of the molecular cavity. N-Heterocyclic carbenes are powerful nucleophiles useful both for catalytic carbon-carbon bond formation and as ligands for transition metals such as ruthenium. The macrocyclic ligand is designed to hold transition metals firmly in its interior where selective alkene metathesis reactions take place. Current ruthenium carbene catalysts display high chemoselectivity (preference for alkenes), but some of their key shortcomings are addressed by this research, including decomposition, lifetime of a key catalytic intermediate, and selectivity. The restrictive nature of the macrocycle is expected to limit decomposition pathways and will display size selectivity for its chemical reactants, an unknown type of selectivity in the alkene metathesis reaction. Alkene metathesis is an important reaction for the synthesis of small molecules, materials, and for energy applications and is used in large-scale industrial applications, the synthesis of pharmaceuticals, and in medicinal chemistry for drug discovery.With the support of the Chemical Catalysis Program in the Chemistry Division at the National Science Foundation, Professor Steven T. Diver and his research team access new chemical catalysts with a wide range of applications based on the metal occupying the interior of the cavity. Fundamental properties of the strong nucleophilic ligand are investigated in this controlled environment. The investigation of new ruthenium carbene catalysts is expected to produce more durable catalysts for applications in sustainable energy. For example, higher lifetime ruthenium carbene catalysts are critical in producing biodiesel fuel that are economically-viable. The outreach component seeks to increase awareness of chemistry as an experimental science to youth through a catalysis project for high school students and for K-12 students through a chemistry merit badge day, relying on high school students and graduate students to lead activities. Kinetics experiments are ideal to illustrate how natural phenomenon can be controlled through experiment and how data can be presented. Catalysts that display increased activities, longer lifetimes, and higher selectivities are in demand and alkane metathesis, the reaction under scrutiny in this research project, is used as a tool to make probes and dyes for chemical biology. Encapsulation of ruthenium carbenes represents a new approach to controlling selectivity and improving stability of a catalyst by limiting bimolecular decomposition. This concept may prove broadly useful to other metal-catalyzed applications.