The reaction of 3-iminoprop-1-enylamines 1 with pentacarbonyl(1-methoxyprop-2-enylidene)chromium(O) complexes leads stereoselectively to substituted 5H-6,7-dihydroazepines in high yields; the process takes place at low temperature and is thought to involve a tandem imine cyclopropanation-Cope rearrangement.