The 5-endo iodine-promoted ring closure of 4-allyl-4-(alkylamino)cyclohexanone derivatives gives the corresponding 1-azaspiro[4.5]decanes in good yields. The reaction was tested with enantiopure homoallylamines to evaluate the diastereoselectivity of the process and to provide a route for possible intermediates to the natural products embodying this azabicyclic ring.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)