Benzimidazolium‐ and Benzimidazolilydene‐Capped Cyclodextrins: New Perspectives in Anion Encapsulation and Gold‐Catalyzed Cycloisomerization of 1,6‐Enynes

• Published in: Chemistry : a European journal Vol. 24; no. 68; pp. 17921 - 17926
• Main Authors: Kaya, Zeyneb, Andna, Lucile, Matt, Dominique, Bentouhami, Embarek, Djukic, Jean‐Pierre, Armspach, Dominique
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 05-12-2018; Wiley-VCH Verlag
• Subjects: Anions; catalysis; Chemical Sciences; Chemistry; Cyclodextrin; Cyclodextrins; Enantiomers; Gold; Intermediates; Isomerization; N-heterocyclic carbenes; Receptors; gold; catalysis; anions; cyclodextrin; N-heterocyclic carbenes
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201804710

A new way of introducing a N‐heterocyclic carbene cap onto cyclodextrins has been devised. The benzimidazolium intermediates were found to behave as receptors towards cavity matching anions. The corresponding C1‐ and C2‐symmetrical regioisomeric carbene gold(I) complexes have been tested in a benchmark asymmetric cycloisomerization of 1,6‐enynes. Up to 50 % ee was achieved for the enantioselective cycloisomerization of N‐allyl‐4‐methyl‐N‐(3‐phenylprop‐2‐yn‐1‐yl)benzenesulfonamide.
Permethylated cyclodextrins equipped with a benzimidazolium handle behave as receptors towards medium‐sized anions. They could be directly converted to NHC gold(I) complexes that act as precatalysts for the asymmetric cycloisomerization of 1,6‐enynes.