Use of Chiral Lewis Acids and Transition Metal Complexes

2 Use of Chiral Lewis Acids and Transition Metal Complexes 

In 1986, Reetz et al. reported that chiral Lewis acids (B, Al, and ll) promoted the aldol reaction of KSA with low to good enantioselectivity [115]. The following year they also introduced asymmetric aldol reaction under catalysis by a chiral rhodium complex [116]. Since these pioneering works asymmetric aldol reactions of silyl enolates using chiral Lewis acids and transition metal complexes have been recognized as one of the most important subjects in modern organic synthesis and intensively studied by many synthetic organic chemists. 

Interestingly, reaction of ketene TBS acetals under the same conditions forms 

Yamamoto et al. found that chiral borane 47b (R=H), derived from monoacyloxy- 

Corey et al. disclosed that tryptophan-derived oxazaborolidine 47f (R=Bu) is an 

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