Neutral Chiral Tetrakis‐Iodo‐Triazole Halogen‐Bond Donor for Chiral Recognition and Enantioselective Catalysis

• Published in: Chemistry : a European journal Vol. 27; no. 7; pp. 2315 - 2320
• Main Authors: Ostler, Florian, Piekarski, Dariusz G., Danelzik, Tobias, Taylor, Mark S., García Mancheño, Olga
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01-02-2021; John Wiley and Sons Inc
• Subjects: Anions; Catalysis; Chemical bonds; Chemistry; chiral anion recognition; Communication; Communications; Computer applications; DFT; Enantiomers; halogen bonding; Hydrogen; Hydrogen bonding; Inversions; NMR; NMR titration; Nuclear magnetic resonance; organocatalysis; Recognition; Titration; Triazoles; chiral anion recognition; organocatalysis; DFT; NMR titration; halogen bonding
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202005016

Halogen bonding represents a powerful tool in the field of noncovalent interactions. However, applications in enantioselective recognition and catalysis remain almost nonexistent, due in part to the distinct features of halogen bonds, including long covalent and noncovalent bond distances and high directionality. Herein, this work presents a novel chiral tetrakis‐iodo‐triazole structure as a neutral halogen bond donor for both chiral anion‐recognition and enantioinduction in ion‐pair organocatalysis. NMR‐titration studies revealed significant differences in anion affinity between the halogen bonding receptor and its hydrogen bonding parent. Selective recognition of chiral dicarboxylates and asymmetric induction in a benchmark organocatalytic reaction were demonstrated using the halogen bond donor. Inversions in the absolute sense of chiral recognition, enantioselectivity, and chiroptical properties relative to the related hydrogen donor were observed. Computational modeling suggested that these effects were the result of distinct anion‐binding modes for the halogen‐ versus hydrogen‐bond donors.
Halogen bonding interactions at work: This work presents a novel chiral tetrakis‐iodo‐triazole as neutral halogen bond donor able to differentiate chiral dicarboxylates and induce chirality in an anion‐binding catalytic reaction. An inversion of chiral recognition, enantioselectivity and CD spectra compared to its parent hydrogen donor was observed and examined by DFT calculations, providing a hint on relevant halogen donor complex structures in solution.