Bis chiral

Fan developed tunable heterobimetallic potassium(i)-crown ether rho-dium(i) catalysts based on a,o)-bis(chiral phosphite) or a,co-(achiral phosphine-chiral phosphite) polyether ligands (Scheme 2.46). For the asymmetric hydrogenation of enamides, catalysts 79 and 80 that showed coordination to the respective metallacrown ethers with the potassium salt... 

Feng and Hu reported a successful nitroaldol reaction of a-ketophosphonates by using a combination of bis-chiral secondary amide 22 and 2,4-dinitrophenol (23) (Scheme 29.9) [23]. In the proposed transihon state, one of the piperidine moieties is protonated by the acidic additive, which achvates the a-ketophosphonate via hydrogen bonding, and the other piperidine deprotonates nitromethane. With this catalyst system, numerous different nitroaldol compounds may be obtained with high optical purities. A Bu OMe/PhOMe (2 1) solvent mixture seems critical... 

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