Enhancing the Regioselectivity of B(C6F5)3-Catalyzed Epoxide Alcoholysis Reactions Using Hydrogen-Bond Acceptors,ACS Catalysis

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Enhancing the Regioselectivity of B(C6F5)3-Catalyzed Epoxide Alcoholysis Reactions Using Hydrogen-Bond Acceptors
ACS Catalysis ( IF 11.3 ) Pub Date : 2019-09-26 , DOI: 10.1021/acscatal.9b03089
Mihir N. Bhagat , Charmaine K. Bennett , Gao-Fong Chang , Youlong Zhu , Arjun Raghuraman ₁ , Matthew E. Belowich ₂ , SonBinh T. Nguyen , Linda J. Broadbelt , Justin M. Notestein

Affiliation

Epoxide alcoholysis is extensively employed in the synthesis of polymers and chemical intermediates, and it generally requires an acid catalyst for high rates and selectivity. Tris(pentafluorophenyl)borane [B(C₆F₅)₃] is among few catalysts that are selective to primary alcohol products of terminal aliphatic epoxides that do not possess any directing groups. We have previously observed that under many conditions, the reaction regioselectivity increases with conversion. Here, we confirm a prediction from our earlier computational model, and we experimentally demonstrate that this increase is due to a selectivity-enhancing role of the reaction products. We then show that deliberate addition of catalytic amounts of certain diols increases the reaction regioselectivity. Cis-1,2 or 1,3-diols are required to enhance selectivity, consistent with a mechanism where extended hydrogen-bonding networks preferentially organize the reactants. This work presents a route to tune regioselectivity without altering the catalyst backbone and provides another example of the role of H-bonding networks in reactions taking place in protic media.

中文翻译：

使用氢键受体增强B（C ₆ F ₅）₃催化的环氧醇解反应的区域选择性

环氧醇解被广泛用于聚合物和化学中间体的合成中，并且通常需要酸催化剂以实现高速率和选择性。三（五氟苯基）硼烷[B（C ₆ F ₅）₃对少数不具有任何导向基团的末端脂肪族环氧化物的伯醇产物具有选择性的催化剂是其中之一。先前我们已经观察到，在许多条件下，反应区域选择性随转化率而增加。在这里，我们确定了较早的计算模型的预测，并通过实验证明了这种增加是由于反应产物的选择性增强作用所致。然后，我们表明故意添加某些二醇的催化量会增加反应的区域选择性。顺式需要-1,2或1,3-二醇来提高选择性，这与延长的氢键网络优先组织反应物的机理相一致。这项工作提出了在不改变催化剂主链的情况下调节区域选择性的途径，并提供了在质子介质中发生反应中氢键网络的另一个例子。

更新日期：2019-09-26

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