Unsymmetric 1,1-diboryl alkenes bearing one -[BPin] (BPin = pinacolatoboryl) and one -[BDan] (BDan = 1,8-diaminonaphthalatoboryl) substituent each were hydrogenated in high yield and enantioselectivity using C1-symmetric pyridine(diimine) (PDI) cobalt complexes. High activities and stereoselectivities were observed with an array of 2-alkyl, 2-aryl, and 2-boryl-substituted 1,1-diboryl alkenes, giving rise to enantioenriched diborylalkane building blocks. Systematic study of substrate substituent effects identified competing steric and electronic demands in the key activating role of the boron substituents, whereby sterically unencumbered boronates such as -[BDan], -[BCat] (BCat = catecholatoboryl), and -[Beg] (Beg = ethyleneglycolatoboryl) promote the hydrogenation of trisubstituted alkenes by enabling irreversible α-boron insertion pathways to achieve otherwise-challenging hydrogenations of trisubstituted alkenes. Deuterium labeling studies with 1,1-diboryl alkenes support an insertion pathway generating a chiral intermediate with two different boron substituents and cobalt bound to the same carbon.

中文翻译：

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硼活化作用使位阻烯烃的钴催化不对称氢化成为可能

使用 C1-对称吡啶（二亚胺）以高产率和对映选择性氢化分别带有一个 -[BPin]（BPin = pinacolatoboryl）和一个 -[BDan]（BDan = 1,8-diaminonaphthalatoboryl）取代基的不对称 1,1-二硼烷基烯烃(PDI) 钴络合物。用一系列 2-烷基、2-芳基和 2-硼基取代的 1,1-二硼基烯烃观察到高活性和立体选择性，产生对映体富集的二硼基烷烃结构单元。底物取代效应的系统研究确定了硼取代基的关键激活作用中的竞争性空间和电子需求，由此空间上不受阻碍的硼酸盐，如 -[BDan]、-[BCat]（BCat = 儿茶酚硼），和 -[Beg]（Beg = ethyleneglycolatoboryl）通过启用不可逆的 α-硼插入途径来实现三取代烯烃的具有挑战性的氢化，从而促进三取代烯烃的氢化。1,1-二硼基烯烃的氘标记研究支持插入途径，生成手性中间体，其中两个不同的硼取代基和钴结合在同一碳上。