Expedient Access to Normal- and Abnormal- N-Heterocyclic Carbene (NHC) Magnesium Compounds from Imidazolium Salts
Expedient Access to Normal- and Abnormal- N-Heterocyclic Carbene (NHC) Magnesium Compounds from Imidazolium Salts
复制标题
DOI：
10.1002/zaac.201600308
复制
发表时间：
2016-11-01
影响因子：
1.4
通讯作者：
Schuermann, Christian J.
中科院分区：
文献类型：
--
作者：
Ghadwal, Rajendra S.;Rottschaefer, Dennis;Schuermann, Christian J.
咪唑鎓盐（IPrH）Cl（1）和（IPrH）I（2）与MeMgI反应，分别生成了N-杂环卡宾（nNHC）化合物（IPr）MgCl（I）（3）和（IPr）MgI 2（4）[IPr = 1，3-双（2，6-二异丙基苯基）咪唑-2-亚基]。通过采用类似的策略，通过用MeMgI处理C2-芳基化咪唑鎓盐（IPrPh）I（5）来制备特征为异常-NHC [aIPr（Ph）= 1，3-双（2，6-二异丙基苯基）-2-苯基-咪唑-4-亚基]的第一镁化合物（aIPr（Ph））MgI 2（OEt 2）（6）。虽然1和2的去质子化可以在室温下完成，但需要升高的温度以用MeMgI去质子化5。这很可能是由于C4-H的pK（a）值高于C2-H氢原子的pK（a）值。6与KN（SiMe 3）（2）的盐复分解反应干净地导致形成氨基镁衍生物（aIPr（Ph））Mg{N（SiMe 3）（2）}（2）（7）。化合物3、4、6和7通过元素分析和NMR光谱研究表征。通过单晶X射线衍射分析确定了3、4和6的分子结构。
Treatment of imidazolium salts (IPrH)Cl (1) and (IPrH)I (2) with MeMgI leads to the formation of normal N-heterocyclic carbene (nNHC) compounds (IPr)MgCl(I) (3) and (IPr)MgI2 (4) [IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene], respectively. By employing a similar strategy, the first magnesium compound (aIPr(Ph))MgI2(OEt2) (6) featuring an abnormal-NHC [aIPr(Ph) = 1,3-bis(2,6-diisopropylphenyl)-2-phenyl-imidazol-4-ylidene] is prepared by the treatment of a C2-arylated imidazolium salt (IPrPh)I (5) with MeMgI. While the deprotonation of 1 and 2 can be accomplished at room temperature, an elevated temperature is required to deprotonate 5 with MeMgI. This is most likely due to the higher pK(a) value of the C4-H than that of the C2-H hydrogen atom. Salt metathesis reaction of 6 with KN(SiMe3)(2) cleanly leads to the formation of a magnesium amide derivative (aIPr(Ph))Mg{N(SiMe3)(2)}(2) (7). Compounds 3, 4, 6, and 7 were characterized by elemental analyses and NMR spectroscopic studies. The molecular structures of 3, 4, and 6 were determined by single-crystal X-ray diffraction analyses.