Serial double nucleophilic addition of amines to the imidazole nucleus

2-(1-Chloro-2,2-dimethylpropyl)-1-methyl-1H-imidazole hydrochloride (2a·HCl) was treated with an excess of N,N-dimethylamine at room temperature to give an abnormal addition product, 4,5-bis(N,N-dimethylamino)-1-methyl-2-(2,2-dimethylpropyl)-2-imidazoline (4a), in 74.2% yield together with a normal SN2 product, 2-(1-N,N-dimethylamino-2,2-dimethylpropyl)-1-methyl-1H-imidazole (3a), in 15.0% yield. The former might be evolved from a serial double nucleophilic addition of the secondary amine molecules to the imidazole nucleus, which has been generally considered as an electron-excessive and stable aromatic ring.