Me6TREN was prepared according to the method reported in the literature [52]. The procedure was as follows: first, 30 mL of a methanol solution of 3.0 M HCl was slowly added dropwise to a 50 mL methanol solution containing 4.0 mL (0.027 mol) of tris(2-aminoethyl)amine. After the reaction mixture was stirred at room temperature for 1 hour, the precipitate was collected by filtration and washed three times with 50 mL of methanol to give 6.72 g (0.026 mol) of ClNH3CH2CH2)3NHCl in 98% yield. Subsequently, 6.72 g of ClNH3CH2CH2)3NHCl, 10 mL of distilled water, 50 mL of formic acid and 46 mL of aqueous formaldehyde were mixed. The mixture was heated in an oil bath at 120°C with stirring for 6 hours. Upon completion of the reaction, the volatile components were removed by rotary evaporation. To the solid residue was added 100 mL of a 10 wt% aqueous NaOH solution. The resulting aqueous phase was extracted four times with 100 mL of ether. The organic layers were combined, dried with anhydrous NaOH and concentrated by rotary evaporation. Finally, 6.0 g of colorless oily product was obtained in 89% yield by vacuum distillation at 62 °C. The structure of the product was confirmed by 1H NMR (CDCl3, 400 MHz): δ 2.20 (s, 18H, CH3); δ 2.3-2.37 (m, 6H, CH2); δ 2.56-2.60 (m, 6H, CH2).
