New Developments in EnantioselectiveBrønsted Acid Catalysis
241
Fig. 11. Conceivable catalytic cycle of the Brønsted-acid catalyzed Mannichaza-Michael-reaction
matic substituted isoquinuclidines demonstrates again the power of noncovalent Brønsted acid catalysis. The special feature of this Mannichaza-Michael reaction is the effective interplay of an achiral and a chiral Brønsted acid which, simultaneously in a cooperative fashion activate the enone and aldimine. This enables an asymmetric reaction
process, thereby, forming the desired isoquinuclidine products with the
generation of three new stereocenters in a highly stereoselective manner
(Rueping and Azap 2006).
11
Asymmetric Brønsted Acid Catalyzed Carbonyl
Activation: The First Organocatalytic
Electrocyclic Reaction
Within the field of chiral ion pair catalysis only aldimines and ketoimines had been activated so far. However, we have recently been successful in the activation of both the electrophile, as well as the nucleophile in a new double Brønsted acid catalyzed reaction.
241
Fig. 11. Conceivable catalytic cycle of the Brønsted-acid catalyzed Mannichaza-Michael-reaction
matic substituted isoquinuclidines demonstrates again the power of noncovalent Brønsted acid catalysis. The special feature of this Mannichaza-Michael reaction is the effective interplay of an achiral and a chiral Brønsted acid which, simultaneously in a cooperative fashion activate the enone and aldimine. This enables an asymmetric reaction
process, thereby, forming the desired isoquinuclidine products with the
generation of three new stereocenters in a highly stereoselective manner
(Rueping and Azap 2006).
11
Asymmetric Brønsted Acid Catalyzed Carbonyl
Activation: The First Organocatalytic
Electrocyclic Reaction
Within the field of chiral ion pair catalysis only aldimines and ketoimines had been activated so far. However, we have recently been successful in the activation of both the electrophile, as well as the nucleophile in a new double Brønsted acid catalyzed reaction.