π‐Face Promoted Catalysis in Water: From Electron‐deficient Molecular Cages to Single Aromatic Slides

Abstract Exploiting noncovalent π‐interactions particularly emerging anion‐π interactions to drive efficient catalysis is fascinating. Even with exciting progresses, can anion‐π activation operate in water remains elusive. Here we report the design, synthesis and catalytic studies of a class of water‐soluble electron‐deficient molecular cages and relevant aromatic slide compounds. The prism‐like cages contain three divided, long, cationic aromatic walls which constitute three highly electron‐deficient V‐shape cavities. They were efficiently synthesized in two steps from a parent triformyl cage in gram‐scale. Crystal structure showed the π‐walls bind to the counter bromide through strong anion‐π interactions. Just 5 mol% of cages were effective in catalyzing decarboxylative Aldol reactions of aldehydes and malonic acid half thioesters in water but not in organic solvents, showing a pronounced hydrophobic amplification effect. Meantime, a series of single π‐slides resembling the π‐wall of the cage performed equally well, while those lacking an extended π‐surface were ineffective, highlighting the essential role of electron‐deficient π‐face on promoting the conversion.