London Dispersion in Brønsted Acid Catalysis

立体选择催化过渡态中色散相互作用的评估是一项非常有价值但具有挑战性的任务，迄今为止主要基于理论计算。对于用于Brønsted酸催化的手性binol基磷酸，预计在其立体决定过渡态中分散相互作用的贡献很大。然而，据我们所知，测量这些色散相互作用的实验装置仍然缺失。近年来，我们对手性磷酸与亚胺二元配合物的结构和氢键性质进行了较为详细的研究。此外，我们开发了DTS-hn方法（用光解密过渡态），这是第一个获得活性过渡态组合的实验方法，并将其应用于手性磷酸对亚胺的转移氢化反应。在这个项目中，各种亚胺/手性磷酸催化剂对在其基态结构中的相对色散供体能量将使用色散能量天平进行实验测量。三种不同的实验分散平衡和相应的理论计算计划来评估溶剂效应，氢键的潜在变化或实验误差的贡献。将得到的色散能值与催化剂的合成结果进行比较，并用DTS-hn方法和理论计算进行解释。总的来说，这种结合实验和理论的方法有望评估Brønsted酸催化过渡态中色散相互作用的重要性，以及它们在基态和过渡态结构之间的潜在变化。

The assessment of dispersion interactions in the transition states of stereoselective catalysis is a very valuable but challenging task, which is so far mainly based on theoretical calculations. For the chiral BINOL-based phosphoric acids used in Brønsted acid catalysis strong contributions of dispersion interactions are expected in their stereodecisive transition states. However to our knowledge an experimental set-up to measure the role of these dispersion interactions is still missing. Recently, we got a detailed insight into the structures and hydrogen bond properties of the binary complexes of chiral phosphoric acids with imines. In addition, we developed the DTS-hn method (decrypting transition states with light) the first experimental access to active transition state combinations and applied it to the transferhydrogenation of imines using chiral phosphoric acids. In this project now the relative dispersion donor energies of various imine/chiral phosphoric catalyst pairs in their ground state structures shall be experimentally measured using dispersion energy balances. Three different experimental dispersion balances and accompanying theoretical calculations are planned to assess contributions from solvent effects, potential changes in the H-bonds or experimental error. The derived dispersion energy values will be compared to the synthetic results of the catalyses and interpreted with the help of the DTS-hn method and theoretical calculations. Overall this combined experimental and theoretical approach is expected to give an assessment of the importance of dispersion interactions in the transition states of Brønsted acid catalysis as well as of their potential changes between ground state and transition state structures.