Sodium borohydride (NaBH4, 4.24 g, 112.1 mmol) was slowly added to a solution of N,N'-bis(2,4,6-trimethylphenyl)ethylenediamine hydrochloride (8.0 g, 27.3 mmol) in tetrahydrofuran (THF, 100 mL) at 0 °C. Subsequently, concentrated hydrochloric acid (HCl, 4.5 mL, 2 eq.) was added dropwise over 30 min. After the dropwise addition, the reaction mixture was continued to be stirred at 0 °C for 20 min. Next, 3M hydrochloric acid (250 mL) was carefully added to the reaction flask at 0°C and the mixture was stirred for 1 hour, during which time the temperature was allowed to naturally rise to room temperature. Upon completion of the reaction, the white precipitate was collected by filtration and washed sequentially with water (200 mL) and 5% acetone-ether mixture (150 mL). The resulting product (9.4 g, 93% yield) was a white solid, which was dried under vacuum and prepared for use. The above obtained hydrochloride (8.5 g, 23 mmol) was suspended in triethyl orthoformate (HC(OEt)3, 35 mL, 162 mmol) and 2 drops of formic acid (HCO2H, ca. 1 mol%) was added as catalyst. The reaction mixture was heated to 120 °C and maintained for 5 hours under argon (Ar) protection. At the end of the reaction, it was cooled to room temperature and hexane (200 mL) was added to precipitate the product. After stirring for 1 hour, the white precipitate was collected by filtration, washed with hexane (200 mL) and dried under vacuum to give the final 1,3-bis(2,4,6-trimethylphenyl)imidazole hydrochloride (IMesH2-HCl, 7.6 g, 96% yield).
