Silver-N-Heterocyclic Carbenes in π-Activation: Synergistic Effects between the Ligand Ring Size and the Anion

TY - JOUR

T1 - Silver-N-Heterocyclic Carbenes in π-Activation

T2 - Synergistic Effects between the Ligand Ring Size and the Anion

AU - Frith, Abigail

AU - Clarke, Aimee K.

AU - Heyam, Alex

AU - Lynam, Jason M.

AU - Newman, Paul D.

AU - Unsworth, William P.

AU - Willans, Charlotte E.

N1 - Funding Information: The project was funded through the EPSRC Dial-A-Molecule Interdisciplinary Mobility Fund and a Mary and Alice Smith Scholarship from the University of Leeds. Funding Information: The authors would like to thank the EPSRC Dial-A-Molecule Network and the Mary and Alice Smith Scholarship for funding. Publisher Copyright: © 2024 The Authors. Published by American Chemical Society.

PY - 2024/2/27

Y1 - 2024/2/27

N2 - A series of 12 silver(I)-N-heterocyclic carbene (NHC) complexes were prepared featuring five- (both saturated and unsaturated backbone), six-, and seven-membered ring ligand scaffolds. The N-substituents of the NHCs were diisopropylphenyl in all cases, while the anion was varied between bromide, acetate, and triflate. The complexes were evaluated as catalysts in the spirocyclization of 1-(1H-indol-3-yl)-4-phenylbut-3-yn-2-one to give a spirocyclic indolenine product. To our knowledge, it is the first time that a systematic study has been conducted to examine the effects of both NHC ring size and anion in this type of silver-catalyzed reaction. While the acetate and triflate complexes catalyzed the reaction to 100% conversion, the bromide complexes exhibited a significant ligand/anion effect. Reactions catalyzed by both complexes bearing the five-membered ring NHC ligands and the complex bearing the seven-membered ring NHC ligand stalled after approximately two turnovers. However, the bromide complex bearing the six-membered ring NHC ligand catalyzes the reaction to almost full conversion, similarly to the acetate and triflate complexes. This demonstrates that the NHC ligand ring size can have a dramatic effect in these types of reactions and does not necessarily display a linear correlation.

AB - A series of 12 silver(I)-N-heterocyclic carbene (NHC) complexes were prepared featuring five- (both saturated and unsaturated backbone), six-, and seven-membered ring ligand scaffolds. The N-substituents of the NHCs were diisopropylphenyl in all cases, while the anion was varied between bromide, acetate, and triflate. The complexes were evaluated as catalysts in the spirocyclization of 1-(1H-indol-3-yl)-4-phenylbut-3-yn-2-one to give a spirocyclic indolenine product. To our knowledge, it is the first time that a systematic study has been conducted to examine the effects of both NHC ring size and anion in this type of silver-catalyzed reaction. While the acetate and triflate complexes catalyzed the reaction to 100% conversion, the bromide complexes exhibited a significant ligand/anion effect. Reactions catalyzed by both complexes bearing the five-membered ring NHC ligands and the complex bearing the seven-membered ring NHC ligand stalled after approximately two turnovers. However, the bromide complex bearing the six-membered ring NHC ligand catalyzes the reaction to almost full conversion, similarly to the acetate and triflate complexes. This demonstrates that the NHC ligand ring size can have a dramatic effect in these types of reactions and does not necessarily display a linear correlation.

UR - http://www.scopus.com/inward/record.url?scp=85186068083&partnerID=8YFLogxK

U2 - 10.1021/acs.organomet.3c00476

DO - 10.1021/acs.organomet.3c00476

M3 - Article

AN - SCOPUS:85186068083

SN - 0276-7333

JO - Organometallics

JF - Organometallics

ER -