2,2'-dinitrostilbene (Prepared in house, see page 622)
Tin(II)chloride (Aldrich)
Glacial acetic acid (Aldrich)
Conc. HCl
KOH

To SnCl₂ (15.4 g, 81.9 mmol) suspended in glacial acetic acid (40 ml) was added concentrated HCl until all SnCl₂ had dissolved (~20 ml). To this was added 2,2’-DNS (1.34 g, 4.96 mmol). The mixture was stirred for 15 minutes at room temperature, and then gradually warmed to 70°C. The mixture was stirred at that temperature for 1 h, and then allowed to cool to room temperature. A yellow precipitate (2,2-DAS.2(HCl)) was recovered by filtration, and washed with glacial acetic acid. This was then dissolved in hot water, and basified with KOH, causing a flocculent yellow precipitate to form. After cooling, the precipitate was extracted with Et₂O, and dried over MgSO₄. The solvent was removed in vacuo, and the yellow solid remaining recrystallized from toluene, leaving 2,2’-diaminostilbene as bright yellow flake-like crystals (0.80 g, 77%).

¹H NMR 400 MHz (CDCl₃): δ ppm 7.40 (dd, ⁴J_HH = 1 Hz, ³J_HH = 8 Hz, 2H, ArH), 7.12 (td, ⁴J_HH = 1 Hz, ³J_HH = 8 Hz, 2H, ArH), 7.03 (s, 2H, CH=CH), 6.81 (td, ⁴J_HH = 1 Hz, ³J_HH = 8 Hz, 2H, ArH), 6.72 (dd, ⁴J_HH = 1 Hz, ³J_HH = 8 Hz, 2H, ArH), 5-2.5 (v. br, ~6H, NH₃)

¹³C{¹H} NMR 100 MHz (CDCl₃): δ ppm 143.9, 128.7, 127.2, 124.1, 119.2, 116.2 (Ar) 125.9 (C=C)

EA: found (calc) C: 79.96 (79.97), H: 6.72 (6.71), N: 13.38 (13.32)

MS (EI⁺): m/z 120 (M⁺)

J. Thiele and O. Dimroth, Ber, 1895, 28, 1411-1414.  10.1002/cber.18950280238