10.1016/S0040-4039(00)00257-4
The research investigates the use of amphiphilic calix[6]arene derivatives 1a and 1b as surfactants in Sc(OTf)3-catalyzed Mukaiyama aldol reactions of silyl enol ethers with aldehydes in water. The study finds that these calix[6]arene derivatives can form a hydrophobic microenvironment in the reaction system, which stabilizes labile silyl enol ethers and promotes the reactions. The calix[6]arene derivative 1b, with a hexyl group, performs better than 1a with a butyl group in terms of reaction rates and yields. The results indicate that the alkyl groups on the lower rim of the calix[6]arenes not only stabilize the silyl enol ethers but also promote the aldol reactions in water. The study concludes that calix[6]arene derivatives 1a and 1b are effective surfactants for aqueous Mukaiyama aldol reactions, providing high yields of aldol products.