Iridium-Catalyzed Silylation of Five-Membered Heteroarenes: High Sterically Derived Selectivity from a Pyridyl-Imidazoline Ligand
Iridium-Catalyzed Silylation of Five-Membered Heteroarenes: High Sterically Derived Selectivity from a Pyridyl-Imidazoline Ligand
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DOI：
10.1002/anie.201916015
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发表时间：
2020-02-18
影响因子：
16.6
通讯作者：
Hartwig, John F.
中科院分区：
文献类型：
--
作者：
Karmel, Caleb;Rubel, Camille Z.;Hartwig, John F.
由于键角的不同，五元环上取代基的空间效应不如六元环上的明显。因此，五元杂芳烃反应的区域选择性在许多情况下很差，所述反应的选择性由空间效应决定，例如C-H键的硼基化。我们报道了当[Ir（cod）（OMe）]（2）（cod= 1，5-cyclooctanes）和菲咯啉配体或新的吡啶基咪唑啉配体组合催化时，五元环杂芳烃的硅烷化反应具有高的空间位置选择性，进一步提高了区域选择性。用这些催化剂的甲硅烷基化反应在用先前报道的催化剂进行的C-H键的硼基化形成产物的混合物或不稳定的产物的条件下，从这些环的最空间可及的C-H键处的官能化产生高产率的杂芳基硅烷。杂芳基硅烷产物经历交叉偶联反应和具有ipso选择性的取代反应，以生成带有卤素、芳基和全氟烷基取代基的杂芳烃。
The steric effects of substituents on five-membered rings are less pronounced than those on six-membered rings because of the difference in bond angles. Thus, the regioselectivities of reactions of five-membered heteroarenes that occur with selectivities dictated by steric effects, such as the borylation of C-H bonds, have been poor in many cases. We report that the silylation of five-membered-ring heteroarenes occurs with high sterically derived regioselectivity when catalyzed by the combination of [Ir(cod)(OMe)](2) (cod=1,5-cyclooctadiene) and a phenanthroline ligand or a new pyridyl-imidazoline ligand that further increases the regioselectivity. The silylation reactions with these catalysts produce high yields of heteroarylsilanes from functionalization at the most sterically accessible C-H bonds of these rings under conditions that the borylation of C-H bonds with previously reported catalysts formed mixtures of products or products that are unstable. The heteroarylsilane products undergo cross-coupling reactions and substitution reactions with ipso selectivity to generate heteroarenes that bear halogen, aryl, and perfluoroalkyl substituents.