Synthesis of 5,6-Diaminoacenaphthylene by Reduction of Sterically Crowded Nitro Groups with Sodium Dithionite

Abstract

5,6-Diaminoacenaphthylene was synthesized in four steps from acenaphthene. This seemingly simple molecule provides unique synthetic challenges because it is relatively difficult to reduce the nitro groups and the molecule contains a particularly reactive double bond. It was determined that the only feasible sequence for the synthesis was to nitrate acenaphthene, then brominate, eliminate, and finally selectively reduce. Several reduction methods were attempted before finding one that would completely reduce both nitro groups while leaving the double bond intact.

Key words

nitration - bromination - elimination - reduction - sodium dithionite

• References and Notes

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• 27 5,6-Diaminoacenaphthylene (DAAnl): DNAnl (0.50 g, 2.06 mmol) was dissolved in acetonitrile (300 mL). Sodium dithionite (2.14 g, 12.3 mmol) and sodium bicarbonate (2.09 g, 24.9 mmol) were added to the solution and dissolved with the addition of water (200 mL). The mixture was allowed to stir gently under nitrogen at room temperature for 40 hours. The reaction mixture was diluted with water (1300 mL) and extracted with ethyl acetate (5 × 200 mL). The organic extracts were dried with anhydrous potassium carbonate, filtered, and rotary evaporated to yield a brown solid (68.6 mg, 18%). ¹H NMR (400 MHz, DMSO-d ₆): δ = 7.43 (d, 2 H), 6.70 (s, 2 H), 6.64 (d, 2 H), 5.87 (broad s, 4 H); GC/MS: m/z = 182 (parent ion, base peak). HRMS: m/z calcd for C₁₂H₁₀N₂: 182.0844; found: 182.0846 (error <1.1 ppm).
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