Department of Chemistry, National University of Singapore, 117543, Singapore, Singapore.
Nat Commun. 2020 Feb 7;11(1):765. doi: 10.1038/s41467-020-14543-2.
Double hydroboration of dienes is the addition of a hydrogen and a boryl group to the two double bonds of a diene molecule and represents a straightforward and effective protocol to prepare synthetically versatile bis(boryl)alkanes, provided that this reaction occurs selectively. However, this reaction can potentially yield several isomeric organoboron products, and it still remains a challenge to control the regioselectivity of this reaction, which allows the selective production of a single organoboron product, in particular, for a broad scope of dienes. By employing a readily available cobalt catalyst, here we show that this double hydroboration yields synthetically useful gem-bis(boryl)alkanes with excellent regioselectivity. In addition, the scope of dienes for this reaction is broad and encompasses a wide range of conjugated and non-conjugated dienes. Furthermore, mechanistic studies indicate that this cobalt-catalyzed double hydroboration occurs through boryl-directed chain-walking hydroboration of alkenylboronates generated from anti-Markovnikov 1,2-hydroboration of 1,n-diene.
双硼氢化反应是指在二烯分子的两个双键上分别加上一个氢原子和一个硼基，代表了一种直接有效的方法来制备具有广泛用途的双（硼烷基）烷烃，前提是该反应具有选择性。然而，该反应可能会产生几种异构的有机硼产物，因此仍然存在一个挑战，即控制该反应的区域选择性，以选择性地生成单一的有机硼产物，特别是对于广泛范围的二烯。通过使用易得的钴催化剂，我们在这里展示了这种双硼氢化反应可以以优异的区域选择性得到具有合成用途的偕双（硼烷基）烷烃。此外，该反应的二烯范围广泛，包括广泛的共轭和非共轭二烯。此外，机理研究表明，这种钴催化的双硼氢化反应是通过反马氏规则 1,2-硼氢化生成的烯基硼酸酯的硼基导向链行走硼氢化反应来进行的。
