Regioselective synthesis of substituted piperidine-2,4-diones and their derivatives via Dieckmann cyclisations

A flexible route to piperidine-2,4-diones variously substituted at the 6-, 5,6- and 2,6-positions, both with and without 1-substitution, is described; no N-protective group is required. A related regioselective Dieckmann cyclisation is also described that uses Davies' alpha-methylbenzylamine auxiliary and affords 6-substituted piperidine-2,4-diones enantioselectively. (C) 2015 Elsevier Ltd. All rights reserved.