The diastereoselectivity of electroreductive cyclization reactions can be improved significantly by using electrogenerated lanthanide ions or Mg2+ generated at a sacrificial anode. The ions presumably serve to coordinate with the Lewis base sites found at each end of the substrate chain, thereby establishing two complexes of differing energies. The diastereoselectivity most likely arises as a consequence of competition between transition states that resemble structures 16 and 17. Unfortunately it was not possible to affect any of the processes catalytically. (c) 2006 Elsevier B.V. All rights reserved.