Achiral Lewis Acid-promoted Reactions in Anhydrous Solvent

1 Achiral Lewis Acid-promoted Reactions in Anhydrous Solvent 

In the nineteen-eighties many researchers developed a variety of Lewis acid catalysts of the Mukaiyama aldol reaction. In particular, TrClO4 [23] and TMSOTf [24] effectively promote reaction of silyl enolates with aldehydes or acetals. These studies suggested that introduction of a soft Lewis base such as the CIO4 or OTf anion into the Lewis acidic center should lead to effective catalysts. Based on this concept, further studies have been continued to develop novel Lewis acid catalysts with higher catalytic activity or higher chemo- and stereoselectivity. 

Unlike BF3-OEt2, a catalytic quantity of tris(pentafluorophenyl)borane (B(C6F5)3) 

Lewis Acid Yield (%) anti syn Yield (%) anti syn 

Yamamoto et al. have reported that the exceptionally bulky Lewis acids MAD and 

---