Phosphoric acid catalysis nucleophilic substitution

The appHcation of chiral Bronsted acids in asymmetric catalysis has increased in recent years [6], In 2006, Rueping et al. reported a double Bronsted acid catalyzed reaction of imine 1 and cyclohexenone 2, in which the electrophile was achvated by a chiral phosphoric acid 4 and the nucleophile was activated by an achiral Bronsted acid 5 (Scheme 43.1) (10). Various aromahc and heteroaromatic substituted isoquinuclidines with electron-withdrawing and electron-donating substituents could be isolated in good yields and high enantiomeric ratios (82-88% ee), with exo/endo ratios between 1 3 and 1 9. The reachvity of a broad range of achiral Bronsted adds was examined and the effect on the enantiomeric induchon was obvious (52% ee to 86% ee for the product 3). 

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