N,N,N′-trialkyl-1,8-diaminonaphthalenes:: convenient method of preparation from protonated proton sponges and the first X-ray information

A simple procedure for the synthesis of N,N,N'-trialkyl-1,8-diaminonaphthalenes is described. It consists in partial demethylation (dealkylation) of commercially available proton sponge [1,8-bis(dimethylamino)naphthalene] and some of its derivatives at heating with HBr-KI-DMF system. Limitation, scope and a possible mechanistic pathway for the reaction are discussed. For isomeric 8-dimethylamino-1-methylamino- and 1-dimethylamino-8-methylamino-4-nitronaphthalenes, X-ray measurements have been conducted. The first examples of complete realkylation reactions in the naphthalene proton sponges are reported. (c) 2005 Elsevier Ltd. All rights reserved.