‘Proton sponge’ amides: unusual chemistry and conversion into superbasic 6,7-bis(dimethylamino)perimidines

Starting from 1-acylamino-4,5-bis(dimethylamino)naphthalenes, the first representatives of previously unknown 6,7-bis(dimethylamino)perimidines have been synthesized. In accordance with the electron-donor nature of the heterocyclic rings in these compounds they behave as proton sponges, displaying higher basicity (pKa 8.4–9.3, DMSO) than those of the parent proton sponge (pKa 7.5, DMSO; 18.6, MeCN) and perimidine (pKa 13.6, MeCN). In accord with DFT calculations and proton transfer experiments, 1H-6,7-bis(dimethylamino)perimidines have been shown to exist as neutral rather than zwitterionic tautomers. A number of interesting observations concerning structure, synthesis, and reactivity of 1-acylamino-4,5-bis(dimethylamino)-8-nitronaphthalenes have been made.