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Palladium Complexes of Thio/Seleno‐Ether Containing N‐Heterocyclic Carbenes: Efficient and Reusable Catalyst for Regioselective C‐H Bond Arylation
European Journal of Inorganic Chemistry ( IF 2.2 ) Pub Date : 2020-01-31 , DOI: 10.1002/ejic.201901259 Ramprasad Bhatt 1 , Nattamai Bhuvanesh 2 , Kamal Nayan Sharma 3, 4 , Hemant Joshi 5
European Journal of Inorganic Chemistry ( IF 2.2 ) Pub Date : 2020-01-31 , DOI: 10.1002/ejic.201901259 Ramprasad Bhatt 1 , Nattamai Bhuvanesh 2 , Kamal Nayan Sharma 3, 4 , Hemant Joshi 5
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The synthesis of the novel S,CNHC type half‐pincer ligand precursors (L1 and L2) is described herein by using the atom economy reactions of 1‐(2‐(phenylthio)ethyl)‐1H‐imidazole with benzyl bromide and bromodiphenylmethane, respectively. The analogous reaction of 1‐(2‐(phenylselanyl)ethyl)‐1H‐imidazole with 2‐bromoethyl phenyl sulfide has also resulted in a imidazolium bromide (L3) which is a precursor of novel S,CNHC,Se type pincer ligand. The route of silver‐NHC transmetalation was employed to get the palladium complexes [Pd(L1/L2–HBr)Cl2] (C1 and C2) and [Pd(L3–HBr)Cl]BF4 (C3). The imidazolium bromide (L1–L3) and palladium complexes (C1–C3) were characterized by using multinuclear NMR and HR‐MS. The structure and bonding in the complexes C1 and C2 were validated by X‐ray crystallography. Thermally robust and moisture/air insensitive palladium complexes C1–C3 have been explored in the catalysis of C–H bond arylation of imidazoles. The protocol operates under mild reaction conditions in air with an excellent regioselective C–H bond arylation at C‐5 position in imidazoles. All the complexes were found to be efficient (yield up to 97 % in 12 h) in the catalysis; however, the activating pincer ligand framework containing Pd catalyst C3, was found to be utmost effective among the three catalysts. Only 0.5 mol‐% catalyst loading is required to achieve admirable yield of the desired cross‐coupled products. A wide range of substrates was examined, and the developed protocol was applicable to all derivatives with high functional group tolerance and greater efficiency. More importantly, the catalyst C3 has also been found recyclable up to five cycles with minor decrease in efficiency which is highly desirable feature for the development of economical and sustainable industrial reaction processes. The PPh3 and Hg poisoning tests have established the complete homogeneous nature of the catalysis.
中文翻译：
含N-杂环卡宾的硫/硒醚的钯配合物：区域选择性CH键芳构化的高效且可重复使用的催化剂
本文使用1-（2-（（苯硫基）乙基）-1H-咪唑与苄基溴和溴代二苯甲烷的原子经济反应描述了新型S，C NHC型半钳位配体前体（L1和L2）的合成， 分别。1-（2-（苯基硒基乙基）乙基）-1H-咪唑与2-溴乙基苯基硫化物的类似反应也产生了溴化咪唑鎓（L3），这是新型S，C NHC，Se型钳位配体的前体。采用银-NHC的金属转移途径得到钯络合物[Pd（L1 / L2 -HBr）Cl 2 ]（C1和C2）和[Pd（L3- HBr）Cl] BF 4（C3）。使用多核NMR和HR-MS对溴化咪唑鎓（L1 - L3）和钯配合物（C1 - C3）进行了表征。X射线晶体学验证了配合物C1和C2中的结构和键合。具有热稳定性且对湿气/空气不敏感的钯配合物C1 - C3已在咪唑的C–H键芳基化催化中进行了探索。该方案在空气中温和的反应条件下运行，在咪唑的C-5位置具有出色的区域选择性C–H键芳基化。发现所有的配合物在催化中都是有效的（12小时内产率高达97％）。然而，发现在三种催化剂中，含Pd催化剂C3的活化钳式配体骨架是最有效的。仅需0.5 mol％的催化剂负载量，即可获得所需交叉偶联产物的优异收率。检查了各种各样的底物，并且所开发的方案适用于具有高官能团耐受性和更高效率的所有衍生物。更重要的是，催化剂C3还发现可循环利用多达五个循环而效率略有下降，这对于发展经济和可持续的工业反应过程是非常需要的特征。PPh 3和Hg的中毒测试确定了催化作用的完全均一性。
更新日期：2020-01-31
中文翻译：
含N-杂环卡宾的硫/硒醚的钯配合物：区域选择性CH键芳构化的高效且可重复使用的催化剂
本文使用1-（2-（（苯硫基）乙基）-1H-咪唑与苄基溴和溴代二苯甲烷的原子经济反应描述了新型S，C NHC型半钳位配体前体（L1和L2）的合成， 分别。1-（2-（苯基硒基乙基）乙基）-1H-咪唑与2-溴乙基苯基硫化物的类似反应也产生了溴化咪唑鎓（L3），这是新型S，C NHC，Se型钳位配体的前体。采用银-NHC的金属转移途径得到钯络合物[Pd（L1 / L2 -HBr）Cl 2 ]（C1和C2）和[Pd（L3- HBr）Cl] BF 4（C3）。使用多核NMR和HR-MS对溴化咪唑鎓（L1 - L3）和钯配合物（C1 - C3）进行了表征。X射线晶体学验证了配合物C1和C2中的结构和键合。具有热稳定性且对湿气/空气不敏感的钯配合物C1 - C3已在咪唑的C–H键芳基化催化中进行了探索。该方案在空气中温和的反应条件下运行，在咪唑的C-5位置具有出色的区域选择性C–H键芳基化。发现所有的配合物在催化中都是有效的（12小时内产率高达97％）。然而，发现在三种催化剂中，含Pd催化剂C3的活化钳式配体骨架是最有效的。仅需0.5 mol％的催化剂负载量，即可获得所需交叉偶联产物的优异收率。检查了各种各样的底物，并且所开发的方案适用于具有高官能团耐受性和更高效率的所有衍生物。更重要的是，催化剂C3还发现可循环利用多达五个循环而效率略有下降，这对于发展经济和可持续的工业反应过程是非常需要的特征。PPh 3和Hg的中毒测试确定了催化作用的完全均一性。
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