Shanghai-Hong Kong Joint Laboratory in Chemical Synthesis, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China.
Department of Chemistry and State Key Laboratory of Synthetic Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China.
Nat Commun. 2017 Mar 16;8:14827. doi: 10.1038/ncomms14827.
Carboranes are carbon-boron molecular clusters, which can be viewed as three-dimensional analogues to benzene. They are finding many applications in medicine, materials and organometallic chemistry. On the other hand, their exceptional thermal and chemical stabilities, as well as 3D structures, make them very difficult to be functionalized, in particular the regioselective functionalization of BH vertex among ten similar B-H bonds. Here we report a very efficient iridium-catalysed borylation of cage B(3,6)-H bonds of o-carboranes with excellent yields and regioselectivity using bis(pinacolato)diboron (Bpin) as a reagent. Selective cage B(4)-H borylation has also been achieved by introducing a bulky TBDMS (tert-butyldimethylsilyl) group to one cage carbon vertex. The resultant 3,6-(Bpin)-o-carboranes are useful synthons for the synthesis of a wide variety of B(3,6)-difunctionalized o-carboranes bearing cage B-X (X=O, N, C, I and Br) bonds.
碳硼烷是碳硼分子簇，可以看作是苯的三维类似物。它们在医学、材料和有机金属化学中有着广泛的应用。另一方面，它们异常的热稳定性和化学稳定性，以及 3D 结构，使得它们很难被功能化，特别是在十个类似的 B-H 键中 BH 顶点的区域选择性功能化。在这里，我们报道了一种非常有效的铱催化的 o-碳硼烷笼 B(3,6)-H 键的硼化反应，使用双(频哪醇)二硼（Bpin）作为试剂，具有优异的收率和区域选择性。通过在一个笼碳原子顶点引入一个大体积的 TBDMS（叔丁基二甲基硅基）基团，也实现了选择性的笼 B(4)-H 硼化。所得的 3,6-(Bpin)-o-碳硼烷是合成具有广泛用途的 B(3,6)-二官能化 o-碳硼烷的有用前体，这些 o-碳硼烷具有笼 B-X（X=O、N、C、I 和 Br）键。
