A series of Cr(salen) complexes have been synthesised from 5-substituted-3-bromosalicylaldehydes and trans-1,2-cyclohexanediamine. These have been used to probe the Cr(salen)-mediated asymmetric epoxidation of alkenes. No simple correlation was found between the electronic character of the salen-substituents and the enantioselectivity-multiple oxidation pathways are proposed as a possible explanation. Enantioselectivities of Lip to 90% have been achieved using a novel, synthetically accessible Cr(salen) complex. (C) 2004 Elsevier Ltd. All rights reserved..