General procedure for the synthesis of N,N'-bis(2,4,6-trimethylphenyl)ethane-1,2-diimine from N,N'-bis(2,4,6-trimethylphenyl)ethane-1,2-diamine: (b) Use of NaCNBH3: In a 300 mL round-bottomed flask, add N,N'-bis(2,4,6-trimethylphenyl)ethane-1,2-diimine (3.8 g, 13 mmol ), methanol (100 mL) and NaCNBH3 (4.92 g, 78 mmol). Concentrated hydrochloric acid was added dropwise to maintain the pH of the reaction system below 4. The reaction was stirred at room temperature for 20 h (overnight). Upon completion of the reaction, the reaction solution was diluted with 50 mL of water, adjusted to alkaline with sodium hydroxide solution and extracted well with dichloromethane. The organic layers were combined, dried with anhydrous magnesium sulfate, filtered and concentrated under reduced pressure to remove the solvent to give N,N'-bis(2,4,6-trimethylphenyl)ethylenediamine in 95% yield.
