Ytterbium aqueous Michael reaction

Ding, R., K. Katebzadeh, L. Roman, K.-E. Bergquist and U.M. Lindstrom, Expanding the Scope of Lewis Add Catalysis in Water Remarkable Ligand Acceleration of Aqueous Ytterbium Triflate Catalyzed Michael Addition Reactions, Journal of Organic Chemistry, 71, 352-355 (2006). 

However, during the addition of -keto esters onto enals, ytterbium triflate proved to be an efficient catalyst [171] as in the Michael additions of a-nitro esters [172]. Several water-soluble phosphines gave the corresponding phos-phonium salts in good yields when added to a,j9-unsaturated acids [173] or activated alkynes [174]. With alkynes, vinyl phosphine oxides or alkenes were formed depending on the pH of the aqueous solution. Significantly, the reaction of nitroalkanes with buten-2-one is considerably accelerated when going from... 

The first Lewis acid-catalyzed asymmetric Michael addition in water was developed by Kobayashi et al, who reported ee s up to 83%. Very recent developments show great promise for further improvement of Michael addition reactions in water. In an elegant study, Kaneda and coworkers used montmorillonite-enwrapped metal triflates to execute C—C bond forming Michael additions. When scandium triflate was employed, adducts were obtained in quantitative yield within a 0.5-3 h at or slightly above room temperature. The catalysts were reusable with no appreciable loss in activity.In another recent study, Lind-strdm and coworkers observed a remarkable ligand acceleration effect in aqueous ytterbium triflate-catalyzed Michael additions. A number of 1,2-diamines and 1,2-aminoalcohols were shown to have a positive influence on the rate of the reaction, the most efficient being tetramethylethylenediamine, which induced a nearly 20-fold rate acceleration. 

Ding, R., Katebzadeh, K., Roman, L., Bergquist, K.-E. and Lindstrom, U.M., Expanding the scope of Lewis add catalysis in water remarkable Ugand acceleration of aqueous ytterbium triflate catalyzed Michael addition reactions, /. Org. Chem., 2006,71,352-355. 

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