Institute of Microbial Chemistry (Bikaken), Tokyo, 3-14-23 Kamiosaki, Shinagawa-ku, Tokyo 141-0021, Japan.
Nat Chem. 2017 Jun;9(6):571-577. doi: 10.1038/nchem.2708. Epub 2017 Jan 30.
The expansion of molecular diversity beyond what nature can produce is a fundamental objective in chemical sciences. Despite the rich chemistry of boron-containing heterocycles, the 1,3-dioxa-5-aza-2,4,6-triborinane (DATB) ring system, which is characterized by a six-membered BNO core, remains elusive. Here, we report the synthesis of m-terphenyl-templated DATB derivatives, displaying high stability and peculiar Lewis acidity arising from the three suitably arranged boron atoms. We identify a particular utility for DATB in the dehydrative amidation of carboxylic acids and amines, a reaction of high academic and industrial importance. The three boron sites are proposed to engage in substrate assembly, lowering the entropic cost of the transition state, in contrast with the operative mechanism of previously reported catalysts and amide coupling reagents. The distinct mechanistic pathway dictated by the DATB core will advance not only such amidations, but also other reactions driven by multisite activation.
超越自然产生能力的分子多样性扩展是化学科学的一个基本目标。尽管含硼杂环具有丰富的化学性质，但具有六元 BNO 核的 1,3-二氧杂-5-氮杂-2,4,6-三硼烷（DATB）环系仍然难以捉摸。在这里，我们报告了间三联苯模板 DATB 衍生物的合成，这些衍生物表现出高稳定性和独特的路易斯酸度，这源于三个适当排列的硼原子。我们发现 DATB 在羧酸和胺的脱水酰胺化反应中具有特殊用途，这是一项具有重要学术和工业意义的反应。三个硼位点被认为参与了底物组装，降低了过渡态的熵成本，与先前报道的催化剂和酰胺偶联试剂的作用机制形成对比。由 DATB 核决定的独特机制途径不仅将推进这种酰胺化反应，还将推进其他由多部位活化驱动的反应。
