Podand-Based Dimeric Chromium(III)-Salen Complex for Asymmetric Henry Reaction: Cooperative Catalysis Promoted by Complexation of Alkali Metal Ions

A new kind of podand‐based dimeric salen ligand was synthesized, and its association with potassium cations was investigated by 1H NMR spectroscopy. The corresponding CrIII–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)2C6H3]4B) led to remarkable improvements in yield (by up to 58 %) and enantioselectivity (for example, from 80 % ee to 96 % ee). Potent podands: A new kind of podand‐based chromium(III)–salen dimer catalyst has been synthesized and successfully applied in asymmetric Henry reactions (see scheme; DIPEA=N,N‐diisopropylethylamine). Remarkable supramolecular regulation of catalytic activity and enantioselectivity has been achieved by the association of the oligo(ethylene glycol) chain within the ligand with a potassium cation.