Alternating macrocyclization and polymerization was observed in dynamic nitroaldol reaction systems. The reaction of an aromatic dialdehyde reacting with linear alpha,omega-dinitroalkanes with even numbers of carbon atoms favored the formation of lowellane macrocycles, while the reactions involving dinitrocompounds consisted of odd numbers of carbon atoms promoted polymerization. The folding patterns of the alkyl chains played an important factor in determining the outcome of the reactions.