Ruthenium(II) Complexes of Heteroditopic N-Heterocyclic Carbene Ligands: Efficient Catalysts for C–N Bond Formation via a Hydrogen-Borrowing Strategy under Solvent-Free Conditions
作者:S. N. R. Donthireddy、Praseetha Mathoor Illam、Arnab Rit
DOI:10.1021/acs.inorgchem.9b03049
日期:2020.2.3
are found to be highly efficient for C-N bond formation across a wide range of primary amine and alcohol substrates under solvent-free conditions, and among all of the complexes studied here, catalyst 3a with a mesityl substituent displayed maximum activity. To our delight, catalyst 3a is also effective for the selective mono-N-methylation of various anilines utilizing methanol as a coupling partner,
咪唑-2-亚烷基(ImNHC)和1,2,3-三唑-5-亚烷基(tzNHC)均已发展成为用于均相催化的N-杂环卡宾(NHC)配体的精英基团。为了开发通过氢借用方法将这些配体用于CN键形成反应的高效钌(II)基催化剂,我们利用了与ImNHC和通过CH2间隔基与不同的三唑骨架连接的中型tzNHC供体集成的螯合配体。发现合成的钌(II)配合物3在无溶剂条件下能在各种伯胺和醇底物上高效形成CN键,并且在本文研究的所有配合物中,均显示了具有甲磺酰基取代基的催化剂3a最大的活动。令我们高兴的是,催化剂3a对于利用甲醇作为偶合伴侣的各种苯胺的选择性单-N-甲基化也是有效的,众所周知,甲醇作为偶合伴侣比其他醇相对困难。此外,配合物3a还通过2-氨基苄醇与几种仲醇的反应成功地递送了各种取代的喹啉。重要的是,催化剂3a在所报道的钌(II)络合物中对苯胺的N-苄基化[实现营业额(TON)为50000]和通过使2-