Journal of Molecular Catalysis A-Chemical, Vol.227, No.1-2, 163-172, 2005
Salen ligands derived from trans-1,2-dimethyl-1,2-cyclohexanediamine: preparation and application in oxo-chromium salen mediated asymmetric epoxidation of alkenes
Syntheses of two novel chiral non-racemic salen ligands and four of their chromium(Ill) complexes are described. The ligands were derived from resolved trans-1,2-dimethyl-1,2-cyclohexanediamine. The complexes were evaluated as asymmetric epoxidation catalysts in the stoichiometric asymmetric epoxidation of E- and Z-beta-methylstyrene and proved disappointing. Elecrotrospray MS of the complexes and single crystal X-ray structure determination of one of the salen ligands was performed. This gave insight as to why the catalysts did not perform as expected on the basis of the existance of multiple oxidants in the system. Some additional details of the synthesis of the diamine are also reported. (C) 2004 Elsevier B.V. All rights reserved.