A 500 mL, three-necked round bottom flask was purged with N_2. To the flask was added 3,3’-diaminobenzidine (250 mg, 4.668 mmol, 4 equiv), benzophenone (850.6 mg, 1.167 mmol, 4 equiv, 1.0 equiv per NH₂ functionality), 1,4-diazobicyclo[2.2.2] octane (DABCO) (3.142 g, 28.008 mmol, 24 equiv) and chlorobenzene (100 mL) and the mixture was stirred at room temperature under N₂. Titanium (IV) chloride (7.002 mL, 7.002 mmol, 6 equiv, 1M in toluene) was syringed in portions over 15 minutes. After the addition, the mixture was stirred for another 20 min at room temperature. The flask was then equipped with a reflux condenser, and the reaction was stirred at 125 ºC for 72 hours. The reaction was then cooled to 40 ºC and vacuum filtered through a Buchner funnel equipped with filter paper. The filtrate was concentrated in vacuo. The crude product was dry-loaded onto silica gel (~3x by mass, 750 mg) and purified using column chromatography using a Teledyne ISCO flash chromatograph system on a 12g column (50% chloroform in hexanes for 4 minutes to 100% chloroform for a remaining 11 minutes). Benzophenone eluted first, and the yellow/orange product eluted second. The product was verified by thin layer chromatography (R_f =0.12) using 100% chloroform and the fractions were concentrated to yield an orange solid (590 mg, 6.779 mmol, 29% yield).

¹H NMR (DMSO, 400 MHz): δ 7.58 - 7.55 (m, 8H), 7.46 - 7.43 (m, 4H), 7.40 - 7.37 (m, 8H), 7.32 - 7.28 (m, 12H), 7.03 - 6.97 (m, 8H), 6.67 (dd, J = 8, 2 Hz, 2H), 6.42 (d, J = 2 Hz, 2H), 6.35 (d, J = 8 Hz, 2H).

¹³C NMR (DMSO, 400 MHz): δ 167.496, 167.268, 142.433, 141.127, 139.481, 139.480, 136.748, 136.702, 134.531, 131.207, 129.332, 129.241, 129.150, 129.021, 128.975, 128.747, 128.520, 128.529, 121.043, 118.159.

IR (cm^-1): 1633 (C=N)

Mass Spec: Calculated – 870.3722 g/mol; Observed – 871.3687 g/mol

Vitaku, E.; Dichtel, W. R. J. Am. Chem. Soc. 2017, 139, 12911-12914.