0.5 moles (ca. 103.1 g) of 1,4-p-phenylenediamine sulfate I, 1.1 moles (ca. 231 g) of analytically pure trifluoroacetic anhydride, 1.6 moles (ca. 162 g) of triethylamine, and 250 ml of analytically pure dichloromethane, were added to the reactor and stirred thoroughly for 1 hour at room temperature. Filtration gave 142.5 g of N1,N4-ditrifluoroacetyl-p-phenylenediamine II.
N1,N4-ditrifluoroacetyl-p-phenylenediamine II (60.3 g, 0.2 mol) was added to 300 ml of analytically pure acetic anhydride and stirred thoroughly to form a suspension. 25 mL of analytically pure concentrated nitric acid was added dropwise to the reaction system at room temperature. Stirring was continued for 6 hours after the addition. The reaction solution was then filtered and the filter cake was washed once with 200 ml of water and once with 200 ml of analytically pure ethyl acetate. After sufficient drying, 36.3 g of N1,N4-ditrifluoroacetyl-2-nitro-p-phenylenediamine III was obtained.
The 36.3 g of N1,N4-ditrifluoroacetyl-2-nitro-p-phenylenediamine III was mixed into the reaction solution. -2-nitro-p-phenylenediamine III, 53 g of sodium carbonate and 400 mL of water were added to the reactor and heated to reflux for 1 hour. At the end of the reaction the reaction system was brought down to room temperature. The reaction system was filtered to give 16.1 g of 2-nitro-p-phenylenediamine. The total yield of the three-step reaction was 50%; the product was a reddish black solid with a melting point of 136-137 C.
