Applications of Oxoammonium Salts to Green Organic Reactions

在美国国家科学基金会化学部化学合成项目的支持下，匹兹堡大学的Paul Floreancig教授利用电化学来合成复杂的有机化合物。电化学反应使用电流代替传统的化学物质。化学试剂通常会产生不需要的副产品，因为它们产生的能量过多或过少，无法形成（或破坏）特定的化学键；因为电流可以精确地控制在给定的电势（电压）下，电化学反应可以被调整，以提供所需转化所需的适量能量。通过这种方式，与传统化学反应相比，电化学反应有望减少化学废物。本研究利用电化学技术产生了新的环境友好的合成方法。研究团队与合作者将有机反应发展与理论和电化学技术相结合。新方法的发展说明了利用氧化反应增加分子复杂性的力量。研究团队对追求绿色化学有着坚定的承诺，并且通过这项研究获得的经验教训被用作本科课程中针对环境无害有机合成的例子。该项目使用电化学氧化来推进氧化碳氢键裂解过程，该过程已在Floreancig小组中开发。这项研究用氧铵离子取代了原先用作化学计量试剂的醌类氧化剂。氧铵离子比醌离子更容易通过阳极氧化再生，并且具有其他优点，例如更容易调整反应性和发展不对称变体以进行对映选择性合成的潜力。第一个目标是通过探索氧化剂强度、电极材料和底物氧化电位的影响，优化氧化环化反应中氧铵离子的电化学再生，以实现低催化剂负载。第二个目标是通过实验和理论相结合的方法来深入了解氧铵离子氧化碳氢键裂解的机制细微差别，从而提供有关电荷转移和过渡态几何形状重要性的信息。第三个目标是开发新的转化，可能与氧铵离子，但不是醌，包括环加成反应和动力学决议。通过出版物和研讨会传播结果，Floreancig小组为科学界提供了强大的新转化，有价值的机制见解，以及将电化学与氧化官能化反应相结合的蓝图。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。

Supported by the Chemical Synthesis Program in the NSF Division of Chemistry, Professor Paul Floreancig at the University of Pittsburgh uses electrochemistry to the synthesize complex organic compounds. Electrochemical reactions use electrical currents in place of traditional chemicals. Chemical reagents often produce undesired by-products because they produce too much or too little energy to make (or break) specific chemical bonds; Because electrical currents can be precisely controlled at a given potential (voltage), electrochemical reactions can be tuned to provide just the right amount of energy needed for a desired transformation. In this way, electrochemical reactions promise to reduce chemical waste when compared to traditional chemical reactions. This research produces new environmentally benign synthetic methods using electrochemical techniques. The research team works with collaborators to combine organic reaction development with theory and electrochemical techniques. The new method development illustrate the power of employing oxidation reactions in increasing molecular complexity. The research team has a strong commitment to pursuing green chemistry and lessons learned through this research are used as examples in undergraduate classes directed toward environmentally benign organic synthesis. This project uses electrochemical oxidations to advance the oxidative carbon-hydrogen bond cleavage processes that have been developed in the Floreancig group. The study replaces quinone oxidants, which were originally used as stoichiometric reagents, with oxoammonium ions. The oxoammonium ions are more readily regenerated through anodic oxidation than their quinone counterparts and offer additional advantages, such as easier reactivity tuning and the potential for developing asymmetric variants for enantioselective synthesis. The first objective is to optimize the electrochemical regeneration of oxoammonium ions in oxidative cyclization reactions to allow for low catalyst loading by exploring the impact of oxidant strength, electrode material, and substrate oxidation potential. The second objective is to gain insight into the mechanistic nuances of oxidative carbon-hydrogen bond cleavage by oxoammonium ions through a combined experimental and theoretical approach that provides information on the importance of charge transfer and geometry of the transition states. The third objective is to develop new transformations that are possible with oxoammonium ions but not quinones, including cycloaddition reactions and kinetic resolutions. By disseminating the results through publication and seminars, the Floreancig group provides the scientific community with powerful new transformations, valuable mechanistic insights, and blueprints for interfacing electrochemistry with oxidative functionalization reactions.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.