Asymmetric Anion-π Catalysis of Iminium/Nitroaldol Cascades To Form Cyclohexane Rings with Five Stereogenic Centers Directly on π-Acidic Surfaces.
Anion-π interactions have been introduced to catalysis only recently, and evidence for their significance is so far limited to one classical model reaction in enolate and enamine chemistry. In this report, asymmetric anion-π catalysis is achieved for the first time for a more demanding cascade process. The selected example affords six-membered carbocycles with five stereogenic centers in a single step from achiral and acyclic substrates. Rates, yields, turnover, diastereo- and enantioselectivity are comparable with conventional catalysts. Rates and stereoselectivity increase with the π-acidity of the new anion-π catalysts. Further support for operational anion-π interactions in catalysis is obtained from inhibition with nitrate. As part of the stereogenic cascade reaction, iminium chemistry and conjugate additions are added to the emerging repertoire of asymmetric anion-π catalysis.
Department of Organic Chemistry, University of Geneva , Geneva, Switzerland.
Le
L
Liu
Department of Organic Chemistry, University of Geneva , Geneva, Switzerland.
Yoann
Y
Cotelle
Department of Organic Chemistry, University of Geneva , Geneva, Switzerland.|Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.
Alyssa-Jennifer
AJ
Avestro
Department of Organic Chemistry, University of Geneva , Geneva, Switzerland.
Naomi
N
Sakai
Department of Organic Chemistry, University of Geneva , Geneva, Switzerland.
Stefan
S
Matile