Synthesis of novel cyclohexanediol-derived chiral phosphite ligands and their application in the Cu-catalyzed conjugate addition of organozinc to cyclic enones |
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Authors: | Zeng-Bo Pang Hai-Feng Li Lai-Lai Wang |
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Institution: | a. State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China;
b. University of Chinese Academy of Sciences, Beijing 100039, China |
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Abstract: | A series of novel chiral diphosphite ligands have been synthesized from (1R,2R)-trans-1,2-cyclohexanediol, (1S,2S)-trans-1,2-cyclohexanediol, racemic trans-1,2-cyclohexanediol and chlorophosphoric acid diary ester, and were successfully employed in the Cu-catalyzed asymmetric 1,4-conjugate addition of diethylzinc to cyclohexenone with up to 99% ee. It was found that ligand 1,2-bis(R)-1,1'-binaphthyl-2,2'-diyl]phosphitecyclohexanediol 6a derived from racemic diol skeleton can show similar catalytic performance compared with ligand (1R,2R)-bis(R)-1,1'-binaphthyl-2,2'-diyl]phosphitecyclohexanediol 6a' derived from enantiopure startingmaterial. A significant dependence of stereoselectivity on the type of enone and the ring size of the cyclic enone was observed. Moreover, the configuration of the products was mainly determined by the configuration of the binaphthyl moieties of diphosphite ligands in the 1,4-addition of cyclic enones. |
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Keywords: | Racemic and chiral cyclohexanediol Phosphite ligands Organozinc Cyclic enones Cu-catalyzed conjugate addition |
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