Fluorous pony-tail, catalysts with

Quinine decorated with a fluorous pony-tail (326) has been developed as a catalyst for the Michael addition of a-fluoro-/ -ketoesters ArC0CHFC02Et to A-substituted maleimides. The resulting products with two vicinal chiral centres were obtained with <87% ee and >20 1 dr, and the catalyst was recycled by fluorous solid-phase extraction. ... 

The fluorous biphase catalyst recovery concept was tested by performing nine consecutive reactions in a batch reactor. A total loss of 4.2% of rhodium was detected, and the decreasing 1 b ratio suggested some ligand leaching. The total turnover number reached with the system was 35,000 mole of aldehyde/mole rhodium, with a rhodium loss of 1.18 ppm per mole of aldehyde. Further optimization of this system, i.e. the use ofheavier fluorous solvents and longer pony tails, should decrease the amoimt of catalyst and fluorous solvent leaching. 

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