Chiral NCN Pincer Iridium(III) Complexes with Bis(imidazolinyl)phenyl Ligands: Synthesis and Application in Enantioselective C–H Functionalization of Indoles with α-Aryl-α-diazoacetates,Organometallics

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Chiral NCN Pincer Iridium(III) Complexes with Bis(imidazolinyl)phenyl Ligands: Synthesis and Application in Enantioselective C–H Functionalization of Indoles with α-Aryl-α-diazoacetates
Organometallics ( IF 2.5 ) Pub Date : 2020-06-04 , DOI: 10.1021/acs.organomet.0c00174
Nan Li ₁ , Wen-Jing Zhu ₁ , Juan-Juan Huang ₁ , Xin-Qi Hao ₁ , Jun-Fang Gong ₁ , Mao-Ping Song ₁

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A series of chiral NCN pincer iridium(III) complexes 2a–h with bis(imidazolinyl)phenyl ligands were synthesized via the central aryl C2–H bond activation of the 1,3-bis(2′-imidazolinyl)benzene ligands. The incorporation of a 5-tert-butyl group into the central aryl ring of the ligands was found to markedly improve the efficiency of the desired C2-metalation, leading to an obvious enhancement in the yields of the Ir(III) complexes. Consequently, complexes with a tert-butyl group on the central aryl ring were obtained in 34–47% yields, whereas those without the group were produced in only 13–16% yields. All of the new complexes have been characterized by elemental analysis and ¹H and ¹³C{¹H} NMR spectroscopy. In addition, the molecular structures of complexes 2c, 2d, and 2g′ have been determined by X-ray single-crystal diffraction. 2c and 2d are, indeed, the anticipated six-coordinate pincer Ir(III) complexes. In contrast, 2g′ is a coordinatively unsaturated five-coordinate pincer Ir(III) complex. The Ir(III) complexes were used as the catalysts for the asymmetric C–H insertion reaction of α-aryl-α-diazoacetates with N-protected indoles. With a catalyst loading of 3 mol % and in the presence of 6 mol % of NaBAr_F, a variety of optically active indole derivatives bearing chiral functional groups at the C3 position were obtained in good yields with moderate to good enantioselectivities (up to 86% ee).

中文翻译：

双（咪唑啉基）苯基配体的手性NCN钳铱（III）配合物：合成和在吲哚α-芳基-α-重氮乙酸酯对映体CH官能化中的应用

通过对1,3-双（2'-咪唑啉基）苯配体的中心芳基C2-H键活化，合成了具有双（咪唑啉基）苯基配体的一系列手性NCN钳形铱（III）配合物2a – h。发现将5-叔丁基结合到配体的中心芳基环中可显着提高所需的C 2-金属化的效率，从而导致Ir（III）配合物的产率明显提高。因此，在中心芳基环上具有叔丁基的配合物的收率为34–47％，而没有该基团的配合物的收率仅为13–16％。所有新的配合物均已通过元素分析和¹ H和¹³表征C { ¹ H} NMR光谱。另外，已经通过X射线单晶衍射确定了络合物2c，2d和2g'的分子结构。2c和2d实际上是预期的六坐标钳式Ir（III）配合物。相反，2g'是配位不饱和的五坐标钳子Ir（III）络合物。Ir（III）络合物用作α-芳基-α-重氮乙酸酯与N保护的吲哚的不对称CH插入反应的催化剂。在3 mol％的催化剂负载量和6 mol％的NaBAr _F存在下，以良好的收率获得了具有中等至良好对映选择性（高达86％ee）的各种旋光活性吲哚衍生物，它们在C3位带有手性官能团。

更新日期：2020-06-23

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