Aldol reaction, aqueous media chiral

Sinou and co-workers [73] studied the influence of different surfactants on the palladium-catalyzed asymmetric alkylation of l,3-diphenyl-2-propenyl acetate with dimethyl malonate in presence of potassium carbonate as base and non-water-soluble chiral ligands. Best results in activity and enatioselectivity (> 90% ee) were observed with 2,2 -bis(diphenylphosphino)-l,l -binaphthyl (BINAP) as ligand and cetyltrimethylammonium hydrogen sulfate as surfactant in aqueous medium. Water-stable Lewis acids as catalysts for aldol reactions were developed by Kobayashi and co-workers [74]. An acceleration of the reaction was indicated in presence of SDS as anionic surfactants. An additional promotion could be observed by combination of Lewis acid and surfactant (LASCs = Lewis acid-surfactant-combined catalysts) as shown in Eq. (3). Surfactant the anion of dodecanesulfonic acid. 

In 2013, the Rahman group studied the application of various polar tripeptides for the direct aldol reaction of substituted aromatic aldehydes and aliphatic ketones in an aqueous medium. In the course of their investigations histidine-containing peptide 35 showed the best results for the aldol reactions due to stabilising hydrogen bonding of the side chains of the peptide catalyst (Scheme 13.22b). This catalytic system could be further extended to aldoketoreductase-based mimetic octapeptides for the preparation of chiral p-hydro)yketones in excellent yield and diastereoselectivity and good enantioselectivity. ... 

The O-TMS-diphenylprolinol 103/BzOH catalytic system is also applicable as an organocatalyst of Michael reactions of nitroalkanes with a, i-enals in aqueous medium [117]. However, functionalized task-specific ionic liquids incorporated in the chiral-pyrrolidine unit, apart from being very efficient and versatile organo-catalysts of Michael and some other asymmetric reactions, show much worse behavior in asymmetric aldol reactions, where their performance is inferior to IL-supported catalysts bearing the a-amino acid fragment [118]. 

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