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9-Ethylcarbazole-3-carbaldehyde (10 g, 0.045 mol, available from Aldrich Chemical, Milwaukee, Wis.) was dissolved in 300 ml of methanol under mild heating. Then, a solution of 7.25 g (0.067 mol) of N-phenylhydrazine (from Aldrich) in methanol was added. The reaction mixture was refluxed for 2 hours to form yellowish crystals. The yellowish crystals were filtered off and washed with a large amount of methanol and dried. The yield of the product, 9-ethyl-3-carbazolecarbaldehyde N-phenylhydrazone, was 13.12 g (92%). The melting point was found to be 136–137° C. The 1H-NMR spectrum (100 MHz) of the product in CDCl3 was characterized by the following chemical shifts (δ, ppm): 1.34 (t, J=7.0 Hz, 3H, CH3); 4.23 (q, J=7.0 Hz, 2H, CH2); 6.90–7.64 (m, 8H, Ar), 7.60 (s, 1H, Ar) 7.81 (dd, 1H, Ar), 8.08 (d, 2H, Ar), 8.15 (d, 1H, ═CH). The IR spectrum of the product was characterized by the following absorption frequencies (KBr, cm−1): ν(N—H) 3306, ν(C—H) 2972, ν(arene C—H) 3051, ν(C═C, C—N in Ar) 1602; 1494; 1475; 1237, ν(C—N) 1256, γ(Ar) 815; 747; 731. The mass spectrum of the product was characterized by the following mass peaks (m/z): 314 (90%, M+1); 222 (100%, H5C12–C12H7N—CH═NH).

1. temperatureThe reaction mixture was refluxed for 2 hours
2. customto form yellowish crystals
3. filtrationThe yellowish crystals were filtered off
4. washwashed with a large amount of methanol
5. customdried
6. customto be 136–137° C
7. customThe IR spectrum of the product was characterized by the following absorption frequencies (KBr, cm−1)