The synthesis of new 7-membered diazepanone alkoxyamines [2,2,7,7-tetramethyl-1-(1-phenyl-ethoxy)-[1,4]diazepan-5-one(3) and 2,7-diethyl-2,3,7-trimethyl-1-(1-phenyl-ethoxy)-[1,4]diazepan-5-one (8)] through the Beckmann rearrangement of piperidin-4-one alkoxyamines was developed. Both 3 and 8 were evaluated as initiators and regulators for the nitroxide-mediated radical polymerization of styrene and n-butyl acrylate. 8, a sterically highly hindered alkoxyamine readily available as a crystalline solid, allowed the fast and controlled polymerization and preparation of polymers with low polydispersity indices (1.2-1.4) up to a degree of polymerization of about 100. (C) 2004 Wiley Periodicals, Inc.