A chiral multidentate salan-supported heterobimetallic catalyst for asymmetric Friedel-Crafts reaction

A new hydroxymethyl-pendant salan (3) containing a chiral backbone and an extra 04 cavity has been prepared through a facile one-pot procedure. The ligand has been characterized by ESI-MS, elemental analysis and 2D NMR techniques. To continue our previous work on the catalytically asymmetric F-C reactions using multimetallic complexes involving salan-type ligands, we investigated the applicability of 3 for both asymmetric Henry and F-C reactions, in comparison with previously reported results using salans 1 and 2. It was revealed that although 3 was not a suitable ligand for homometallic copper-catalyzed Henry reaction, it was effective for the hetereobimetallic Cu/Zn-catalyzed asymmetric F-C reaction, affording desired alkylated product with good yield and moderate enantiomeric excess (ee), after screening of various catalyst combinations. (C) 2017 Elsevier B.V. All rights reserved.