Department of Organic Chemistry, University of Geneva, Geneva, Switzerland.
Angew Chem Int Ed Engl. 2016 Nov 7;55(46):14422-14426. doi: 10.1002/anie.201608842. Epub 2016 Oct 14.
Anion-π catalysis, that is the stabilization of anionic transition states on π-acidic aromatic surfaces, has so far been developed with naphthalenediimides (NDIs). This report introduces perylenediimides (PDIs) to anion-π catalysis. The quadrupole moment of PDIs (+23.2 B) is found to exceed that of NDIs and reach new records with acceptors in the core (+70.9 B), and their larger surface provides space to better accommodate chemical transformations. Unlike NDIs, the activity of PDI catalysts for enolate and enamine addition is determined by the twist of their π surface rather than their reducibility. These results, further strengthened by nitrate inhibition and circular dichroism spectroscopy, support an understanding of anion-π interactions centered around quadrupole moments, i.e., electrostatic contributions, rather than redox potentials and charge transfer. The large PDI surfaces provide access to the highest enantioselectivities observed so far in anion-π catalysis (96 % ee).
阴离子-π 催化，即通过π-酸性芳环表面稳定阴离子过渡态，迄今为止一直采用萘二酰亚胺（NDIs）来开发。本报告将苝二酰亚胺（PDIs）引入阴离子-π 催化。PDI 的四极矩（+23.2 B）被发现超过了 NDI，并在核心中与受体一起达到了新的记录（+70.9 B），其更大的表面为更好地容纳化学转化提供了空间。与 NDIs 不同，PDI 催化剂对烯醇化物和烯胺加成的活性取决于其π 表面的扭曲，而不是其还原能力。这些结果，进一步受到硝酸盐抑制和圆二色性光谱的加强，支持了以四极矩（即静电贡献）为中心而不是氧化还原电位和电荷转移的阴离子-π 相互作用的理解。大的 PDI 表面提供了迄今为止在阴离子-π 催化中观察到的最高对映选择性（96%ee）。
