Enantiopure secondary alcohols are fundamental high‐value synthetic building blocks. One of the most attractive ways to get access to this compound class is the catalytic hydroboration. We describe a new concept for this reaction type that allowed for exceptional catalytic turnover numbers (up to 15 400), which were increased by around 1.5–3 orders of magnitude compared to the most active catalysts previously reported. In our concept an aprotic ammonium halide moiety cooperates with an oxophilic Lewis acid within the same catalyst molecule. Control experiments reveal that both catalytic centers are essential for the observed activity. Kinetic, spectroscopic and computational studies show that the hydride transfer is rate limiting and proceeds via a concerted mechanism, in which hydride at Boron is continuously displaced by iodide, reminiscent to an S_N2 reaction. The catalyst, which is accessible in high yields in few steps, was found to be stable during catalysis, readily recyclable and could be reused 10 times still efficiently working.

中文翻译：

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高活性的路易斯酸-铵盐催化剂对酮的对映选择性硼氢化

对映纯仲醇是基本的高价值合成基石。进入这类化合物最吸引人的方法之一是催化硼氢化。我们描述了这种反应类型的新概念，该概念可实现出色的催化转换数（最多15400），与先前报道的最具活性的催化剂相比，催化转换数增加了约1.5–3个数量级。在我们的概念中，质子惰性的卤化铵部分与同一个催化剂分子中的亲氧路易斯酸协同作用。对照实验表明，两个催化中心对于观察到的活性都是必不可少的。动力学，光谱学和计算研究表明，氢化物的转移受到速率的限制，并且通过协同机制进行，其中硼中的氢化物被碘化物连续置换，_N 2反应。该催化剂可在几个步骤中以高收率获得，发现在催化过程中稳定，易于回收并且可以重复使用10次，仍然有效工作。