Pasyukov Dmitry V, Shevchenko Maxim A, Minyaev Mikhail E, Chernyshev Victor M, Ananikov Valentine P
Platov South-Russian State Polytechnic University (NPI), Technology Department, Prosveschenya 132, Novocherkassk, 346428, Russia.
Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospect 47, Moscow, 119991, Russia.
Chem Asian J. 2024 Dec 16;19(24):e202400866. doi: 10.1002/asia.202400866. Epub 2024 Oct 31.
N,N'-Diarylimidazolium salts containing haloalkyl functional groups that are reactive with various nucleophiles are considered to be promising reagents for the preparation of functionalized N-heterocyclic carbene (NHC) ligands, which are in demand in catalysis, materials science, and biomedical research. Recently, 4-chloromethyl-functionalized N,N'-diarylimidazolium salts became readily available via the condensation of N,N'-diaryl-2-methyl-1,4-diaza-1,3-butadienes with ethyl orthoformate and MeSiCl, but these compounds were found to have insufficient reactivity in reactions with many nucleophiles. These chloromethyl salts were studied as precursors in the synthesis of bromo- and iodomethyl-functionalized imidazolium salts by halide anion exchange. The 4-ICH-functionalized products were found to be unstable, whereas a series of novel 4-bromomethyl functionalized N,N'-diarylimidazolium salts were obtained in good yields. These bromomethyl-functionalized imidazolium salts were found to be significantly more reactive towards various N, O and S nucleophiles than the chloromethyl counterparts and enabled the preparation of previously inaccessible heteroatom-functionalized imidazolium salts, some of which were successfully used as NHC proligands in the preparation of Pd/NHC and Au/NHC complexes.
含有可与各种亲核试剂发生反应的卤代烷基官能团的N,N'-二芳基咪唑盐被认为是制备功能化N-杂环卡宾（NHC）配体的有前景的试剂，这些配体在催化、材料科学和生物医学研究中都有需求。最近，通过N,N'-二芳基-2-甲基-1,4-二氮杂-1,3-丁二烯与原甲酸乙酯和MeSiCl的缩合反应，4-氯甲基官能化的N,N'-二芳基咪唑盐变得容易获得，但发现这些化合物在与许多亲核试剂的反应中反应活性不足。这些氯甲基盐作为卤化物阴离子交换合成溴代和碘代甲基官能化咪唑盐的前体进行了研究。发现4-碘甲基官能化产物不稳定，而一系列新型的4-溴甲基官能化的N,N'-二芳基咪唑盐以良好的产率获得。发现这些溴甲基官能化的咪唑盐对各种N、O和S亲核试剂的反应活性明显高于氯甲基对应物，并能够制备以前无法获得的杂原子官能化咪唑盐，其中一些成功地用作制备Pd/NHC和Au/NHC配合物的NHC前体配体。
