Binaphthyl sulfonimides

Several chiral organocatalysts such as chiral squaramide 31, chiral phosphoric acid (S)-32a, and binaphthyl-based chiral sulfonimide (i )-33 have also been successfully applied in the AFC reaction of indoles with N-sulfonyl imines (Scheme 6.14). 

Other chiral Bronsted acid organocatalysts developed more recently include chiral binaphthyl-derived disulfonic acids [162] and sulfonimides [163] and SPINOL-derived phosphoric acids [164]. 

It has also been found that the asymmetric alkylation of indoles with A-sulfonyl imines may be catalysed by a binaphthyl-based chiral sulfonimide. " ... 

N-Boc-protected ethyl trifluoropyruvate imine was effectively used in a F-C reaction with indole derivatives for synthesizing, in high selectivities, quaternary a-amino acids via catalysis with chiral phosphoric acid 26e [64]. A binaphthyl-based chiral sulfonimide [42c] and a chiral squaramide-based hydrogen bond donor [42a] were used as effective catalysts for promoting F-C reaction of indoles with imines. Recently, the F-C alkylation of arenes with glyoxylate imine was described via a chiral phosphoric add (Scheme 35.11) [34]. 

A diammonium salt of chiral l,r-binaphthyl-2,2 -diamine and trifluoromethane-sulfonimide (Tf NH) (5mol% loading) showed excellent catalytic activity and enantioselectivity (88% yield with 92% exo and 91% ee) toward the Diels-Alder reaction of a-acyloxyacroleins with cyclic dienes [69]. Extension of Diels-Alder reactions to a-branched aldehydes was also reported [70]. 

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