Chiral Phosphoric Acid-Ca Catalysts

140c(10mol%) 4A MS, CH2CI2 then NaBH4, MeOH 

Kobayashi et al. developed catalytic asymmetric 1,4-additions using chiral calcium species prepared from calcium isopropoxide and chiral bisoxazoline ligands 39, 166 and 168. They found that calcium pyBOX catalysts could effectively mediate catalytic asymmetric additions of 1,3-dicarbonyl compounds 4 to nitroalkenes 86, N-Boc-imines 138 or unsaturated amides 49 giving products 165,167 and 170, respectively. Neutral coordinative ligands worked well in these reactions, giving a noticeably faster rate of reaction 

Greenwood and A. Earnshaw, Chemistry of the Elements, Butterworth-Heinemann, 2nd edn, 1997 (b) F. A. Cotton, G. Wilkinson and P. L. Gaus, Basic Inorganic Chemistry, Wiley, New York, USA, 3rd edn, 1995. 

CCDC 804337 (89b/Mg(OTf)2) contain the supplementary crystallographic data. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data request/cif. 

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