Jeong Ju Gyeong, Oh Young-Ho, Park Tae Hyun, Lee Sung-Sik, Kim Dong Wook, Lee Sungyul
Department of Chemistry, Inha University, 100 Inha-ro, Nam-gu, Incheon, 402-751, Republic of Korea.
Department of Applied Chemistry, Kyung Hee University, Yongin City, Gyeonggi, 17104, Republic of Korea.
Nat Commun. 2025 Jan 31;16(1):1236. doi: 10.1038/s41467-024-55795-6.
We present experimental probes of contact ion-pair (CIP) S2 reactions for simplest prototype systems by F-NMR spectroscopy. This study provides crucial evidences for the reactions of CIP metal salts facilitated by Lewis base phase transfer catalysts (PTCs) [2,2,2]-cryptand, 18-crown-6, pentaethylene glycols (pentaEGs) and BINOL-based pentaEG. The F-NMR spectra of MF (M = K, Cs) ion-pairs in various solvents are used as fingerprinting tools to identify the CIP CsF/PTC/substrate complexes in S2 reactions. Examination of the prototype reactions demonstrates that the novel CIP mechanism, which is in sharp contrast to the conventional perspectives, may account for the observed phenomenal efficiency of the S2 processes using the alkali metal salts under the influence of various PTCs. In this extremely efficient and selective protocol of wide applicability, the CIP MF is activated by the Lewis base PTCs acting on the counter-cation M to drastically mitigate the latter's retarding Coulomb forces on the adjacent nucleophile F, with or without the participation of hydrogen bonds.
我们通过氟核磁共振光谱法展示了最简单原型体系中接触离子对（CIP）的双分子亲核取代（S2）反应的实验探针。这项研究为路易斯碱相转移催化剂（PTCs）[2,2,2]-穴醚、18-冠-6、五乙二醇（pentaEGs）和基于联萘酚的五乙二醇促进的CIP金属盐反应提供了关键证据。各种溶剂中MF（M = K、Cs）离子对的氟核磁共振光谱被用作指纹识别工具，以识别S2反应中的CIP CsF/PTC/底物络合物。对原型反应的研究表明，与传统观点形成鲜明对比的新型CIP机制，可能解释了在各种PTCs影响下使用碱金属盐时S2过程中观察到的显著效率。在这种具有广泛适用性的极其高效和选择性的方案中，CIP MF通过作用于抗衡阳离子M的路易斯碱PTCs被激活，以极大地减轻后者对相邻亲核试剂F的阻碍库仑力，无论是否有氢键参与。
