title: Podand-based dimeric chromium(III)-salen complex for asymmetric Henry reaction: cooperative catalysis promoted by complexation of alkali metal ions.
abstract: A new kind of podand-based dimeric salen ligand was synthesized, and its association with potassium cations was investigated by (1) H NMR spectroscopy. The corresponding Cr(III) -salen dimer was assembled by a supramolecular host-guest self-assembly process and was then used as a catalyst in highly efficient and enantioselective asymmetric Henry reactions. Regulation by KBArF (BArF =[3,5-(CF3 )2 C6 H3 ]4 B) led to remarkable improvements in yield (by up to 58 %) and enantioselectivity (for example, from 80 % ee to 96 % ee).
authors.affiliation: Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Sciences (CAS), Beijing 100190 (P.R. China); Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072 (P.R. China).
authors.forename: Guang-Hui
authors.initials: GH
authors.lastname: Ouyang
authors.forename: Yan-Mei
authors.initials: YM
authors.lastname: He
authors.forename: Qing-Hua
authors.initials: QH
authors.lastname: Fan
keywords: Henry reaction; asymmetric catalysis; host-guest systems; podands; supramolecular catalysis