Facile preparation and the crystal structure of -dialkyl-2,6-pyridinedimethanaminium halide

Kobayashi, Toru ; Yaita, Tsuyoshi; Sugo, Yumi; Suda, Hiroki*; Suzuki, Shinji*; Fujii, Yuki*; Nakano, Yoshiharu*

A facile preparation and the crystal structures of -dialkyl-2,6-pyridinedimethanaminium halides were described. Direct substitution reactions were convenient to prepare specifically secondary diaminesusing 2,6-bis(chloromethyl)- pyridine and 10 equivalents molar of primary alkylamines. Hydrogen halidesalts were obtained in good yields and the crystal structures of three -dialkyl-2,6-pyridinedimethanaminium salts were determined by the X-ray diffraction method. A cancroid structure around the pyridine ring was observed commonly in the three salts. Acidity constants of the three salts were determined. Since the pKa values of the salts were slightly smaller than those of several commontriamines previously reported, the acidities did not correlate with the cancroid structure directly. This isprobably due to electrostatic interaction of the two protonated amino groups, furthermore the central pyridine nitrogen was not protonated in all the ligands.