Development of highly effective encapsulating surfactants for Mukaiyama aldol reactions in water

Amphiphilic calix[6]arene derivatives 1a-b and calix[4]arene 1d-1e, as well as aliphatic (2a-b) and aromatic (2c-2d) anionic surfactants, were studied for their encapsulating ability in stabilizing water-sensitive compounds. They were found to be efficient surfactants for Sc(OTf)₃-catalyzed Mukaiyama aldol reactions of labile enol ethers with aldehydes in water. The results indicate that a hydrophobic microenvironment was formed in the reaction system with either the amphiphilic calix[6]arene derivatives or the simple aromatic surfactants, which could encapsulate and stabilize some labile silyl enol ethers and thus promote the reactions.