Helical Chiral N‐Heterocyclic Carbene Ligands in Enantioselective Gold Catalysis. Issue 17 (28th February 2022)

• Record Type: Journal Article
• Authors: Pallova, Lenka; Abella, Laura; Jean, Marion; Vanthuyne, Nicolas; Barthes, Cécile; Vendier, Laure; Autschbach, Jochen; Crassous, Jeanne; Bastin, Stéphanie; César, Vincent
• Is Part Of: Chemistry. Volume 28:Issue 17(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-02-28
• Subjects: asymmetric catalysis -- chirality -- gold -- helicenes -- N-heterocyclic carbenes; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.202200166
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: The first chiral helicene‐NHC gold(I) complexes efficient in enantioselective catalysis were prepared. The L‐shaped chiral ligand is composed of an imidazo[1, 5‐ a ]pyridin‐3‐ylidene (IPy) scaffold laterally substituted by a configurationally stable [5]‐helicenoid unit. The chiral information was introduced in a key post‐functionalization step of a NHC‐gold(I) complex bearing a symmetrical anionic fluoreno[5]helicene substituent, leading to a racemic mixture of complexes featuring three correlated elements of chirality, namely central, axial and helical chirality. After HPLC enantiomeric resolution, X‐ray crystallography and theoretical calculations enabled structural and stereochemical characterization of these configurationally stable NHC‐gold(I) complexes. The high potential in asymmetric catalysis is demonstrated in the benchmark cycloisomerization of N‐tethered 1, 6‐enynes with up to 95 : 5 er. Abstract : Helical‐NHC ligands were for the first time used as chiral ligands in enantioselective gold(I) catalysis. The introduction of the chirality was realized in a key post‐functionalization step and led to the generation of a chiral NHC laterally substituted by a new configurationally stable [5]‐helicoidal moiety. This structural design allowed good activities and high ee values in the gold‐catalyzed cycloisomerization of N‐tethered enynes.