Reactivity of 1,3-dichloro-1,3-bis(dimethylamino)-propenium salts with primary amines

Abstract

1,3-Dichloro-1,3-bis(dimethylamino)propenium salts react with primary amines to give different products depending on the structure of the amine. Reactions in which the primary amine is bonded to a tertiary carbon (tert-butylamine and 1-adamantylamine) result in 1,1-bis(dimethylamino)-3,3-bis(alkylamino)propenium salts which form via a 1,3-dimethylamino shift. In contrast, the reactions in which the primary amine is bonded to a secondary carbon (cyclohexylamine, cyclopentylamine, and sec-butylamine) result in 1-(ylidene)amino-1,3-bis(dimethylamino)propenium salts which form via an intramolecular hydride shift. All of the synthesized compounds have been fully characterized using spectroscopic methods, including single crystal X-ray diffraction. Finally, the mechanisms of the intramolecular rearrangements have been investigated computationally at the ωB97X-D/6-311G(d,p) level of theory, suggesting that the reactions proceed through putative keteniminium species.