Sutar Revannath L, Engelage Elric, Stoll Raphael, Huber Stefan M
Fakultät für Chemie und Biochemie, Ruhr-Universität Bochum, Universitätsstrasse 150, 44801, Bochum, Germany.
Angew Chem Int Ed Engl. 2020 Apr 20;59(17):6806-6810. doi: 10.1002/anie.201915931. Epub 2020 Mar 18.
Even though halogen bonding-the noncovalent interaction between electrophilic halogen substituents and Lewis bases-has now been established in molecular recognition and catalysis, its use in enantioselective processes is still very rarely explored. Herein, we present the synthesis of chiral bidentate halogen-bond donors based on two iodoimidazolium units with rigidly attached chiral sidearms. With these Lewis acids, chiral recognition of a racemic diamine is achieved in NMR studies. DFT calculations support a 1:1 interaction of the halogen-bond donor with both enantiomers and indicate that the chiral recognition is based on a different spatial orientation of the Lewis bases in the halogen-bonded complexes. In addition, moderate enantioselectivity is achieved in a Mukaiyama aldol reaction with a preorganized variant of the chiral halogen-bond donor. This represents the first case in which asymmetric induction was realized with a pure halogen-bond donor lacking any additional active functional groups.
尽管卤键（亲电卤素取代基与路易斯碱之间的非共价相互作用）现已在分子识别和催化中得到确立，但其在对映选择性过程中的应用仍极少被探索。在此，我们展示了基于两个带有刚性连接手性侧链的碘代咪唑鎓单元的手性双齿卤键供体的合成。利用这些路易斯酸，在核磁共振研究中实现了对外消旋二胺的手性识别。密度泛函理论计算支持卤键供体与两种对映体的1:1相互作用，并表明手性识别基于卤键配合物中路易斯碱的不同空间取向。此外，在手性卤键供体的预组织变体参与的 Mukaiyama 羟醛反应中实现了适度的对映选择性。这代表了首例使用缺乏任何额外活性官能团的纯卤键供体实现不对称诱导作用（的情况）。
