Dimethylamide of p-aminobenzoic acid 6.00g (36.54 mmol) and (PhO)2C=N-CN 10.14g (Aldrich; 42.56 mmol) in anhydrous THF 60mL was refluxed under nitrogen on a 80C oil bath for 2 days. [Note 1] The cooled reaction mixture was concentrated on rotovap. The obtained oily residue was diluted with anh. THF 20mL and cooled to 0C. Anhydrous hydrazine 1M solution in THF 60mL (Aldrich) was added, the mixture was stirred on ice for 15 min and at ambient temperature for 20 min, then placed on a 70C oil bath and refluxed under nitrogen for 30 min. The reaction mixture was cooled to room temperature, the precipitated product was collected by filtration and washed with MTBE (tBuOMe), then dried by suction and on highvac. Y= 10.48g of a white fluffy powder (90% th; as a 1:1 solvate with THF)
1H(d6-DMSO, 400MHz): 11.22 (br s, 1H), 8.94 (br s, 1H), 7.52(app d, 8.6Hz, 2H); 7.27(app d, 8.6Hz, 2H), 5.92(br s, 2H); 3.60(m, 4H, THF); 2.95(s, 6H), 1.76(m, 4H, THF); 13C(d6-DMSO, 100MHz): 170.47, 128.29, 114.44, 67.00(THF), 25.11(THF)
Note 1: 1 day reflux would have been enough.
Note 2: The starting aniline was prepared by hydrogenation of dimethylamide of p-nitrobenzoic acid (5% Pt-C, H2 baloon, EtOAc), which was obtained from p-nitrobenzoyl chloride and 40% aq. dimethylamine in THF, at -15 C. The yield was 90% over two steps.