Achiral Bronsted and Lewis Acid-promoted Reactions

Achiral Bronsted and Lewis Acid-promoted Reactions 

Studies in the nineteen-eighties revealed that some Maimich-type reactions of imines with silyl enolates can be controlled with high diastereoselectivity, and that use of a chiral auxiliary enables highly enantioselective synthesis of -aminocarbo-nyl compounds [186]. Some Lewis acids, for example TMSOTf and zinc halides, were also found to be effective in catalytic quantities [187-190] although the original method requires a stoichiometric amount of TiCU [185]. In the last decade, further progress has been made by development of new acid catalysts. 

Kobayashi et al. have reported that the three-component Mannich-type reaction 

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