(1E,2E)-N 1 ,N A slightly modified literature procedure 3 was used to synthesize a4. To a round-bottom equipped with a stirbar, EtOH (0.5 M), 2,3-butanedione (1 eq), substituted aniline a1 (2 eq), and several drops of formic acid was added. This solution was allowed to heat at 70 ºC. A yellow precipitate is formed after a few hours. After stirring for 15 hours, the EtOH was evaporated and the product a4 was purified by column chromatography on silica gel (pentane:DCM, 20:1) as a yellow solid. yield: 70%. A slightly modified literature procedure was used to synthesize a5. To a mixture of 2,6-dibenzhydryl-4-(tert-butyl)aniline a2 (6.4 mmol, 3.1 g) and 2,3butadione (3.2 mmol, 276 mg) in toluene (20 mL), a catalytic amount of p-toluene sulfonic acid (0.15 g) was added and heated to 80 ºC for 9 h and then the reaction was refluxed using Dean-stark trap for another 72 h. After all the volatile was evaporated under reduced pressure and the crude product was purified by column chromatography using basic alumina with pentane/ethyl acetate (v/v = 500: 2) as eluent to afforded the a5 as a yellow powder (2.2 g, 68%).