O=P(Cl)(Cl)Cl.[CH2:6]([N:8]1[C:20]2[CH:19]=[CH:18][CH:17]=[CH:16][C:15]=2[C:14]2[C:9]1=[CH:10][CH:11]=[CH:12][CH:13]=2)[CH3:7].[C:21]([O-:24])(=O)C.[Na+].CN([CH:29]=[O:30])C>O>[CH2:6]([N:8]1[C:20]2[CH:19]=[CH:18][C:17]([CH:29]=[O:30])=[CH:16][C:15]=2[C:14]2[C:9]1=[CH:10][CH:11]=[C:12]([CH:21]=[O:24])[CH:13]=2)[CH3:7]A 271 ml quantity of DMF (3.5 mol) was added to a 1-liter, 3-neck round bottom flask equipped with a mechanical stirrer, a thermometer, and an addition funnel. The contents were cooled in a salt/ice bath. When the temperature inside the flask reached 0° C., 326 ml of POCl3 (3.5 mol) was slowly added. During the addition of POCl3, the temperature inside the flask was not allowed to rise above 5° C. After the addition of POCl3, the reaction mixture was allowed to warm to room temperature. After the flask warmed to room temperature, N-ethylcarbazole (93 g) in 70 ml of DMF was added, and then the flask was heated to 90° C. for 24 hours using a heating mantle. Then, the reaction mixture was cooled to room temperature, and the reaction mixture was added slowly to a cooled 4.5 liter beaker containing a solution comprising 820 g of sodium acetate dissolved in 2 liters of water. The beaker was cooled in an ice bath and stirred for 3 hours. The brownish solid obtained was filtered and washed repeatedly with water, followed by a small amount of ethanol (50 ml). After washing, the resulting product was recrystallized once from toluene using activated charcoal and dried under vacuum in an oven heated at 70° C. for 6 hours to obtain 55 g (46% yield) of N-ethyl-3,6-diformylcarbazole. The product was characterized with 1H-NMR (250 Hz, in CDCl3) to obtain the following delta values in ppm: 10.12 (s, 2H), 8.63 (s, 2H), 8.07 (d, 2H), 7.53 (d, 2H), 4.45 (m, 2H), 1.53 (t, 3H).
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