The conversion of 1,3-bis-(6-amino-pyridin-2yl)-urea (1) with N',N'-carbonyldiimidazole at high temperatures in DMSO yielded a mixture of defined cyclic trimers and tetramers. On the basis of model reactions, exchange reactions were evidenced, which convert the cyclic tetramer into a stable cyclic trimer. Linear even numbered oligomers were obtained in acetone under reflux where side reactions were suppressed. The pronounced tendency of cyclization is attributed to a preferred folded conformation of the urea bond between two pyridyl units.
|Number of pages||8|
|Journal||Journal of organic chemistry|
|Publication status||Published - 2 Nov 2012|
- Oligopyridine-dicarboxamide strands, Single helical structures, Oligo(phenanthroline dicarboxamide)s, Heterocyclic ureas, Foldamers, Naphthyridine, System, Amide