Compound 3

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Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.

6-(Bromomethyl)-6'-(((6'-methyl-[2,2'-bipyridin]-6-yl)methoxy)methyl)-2,2'-bipyridine S1 (Harding, M. M. et al. Synthesis of unsubstituted and 4,4′-substituted oligobipyridines as ligand strands for helicate self-assembly. Helv. Chim. Acta. 74, 594 (1991)) (461 mg, 1.0 mmol) and potassium phthalimide S2 (1.1 g, 6.0 mmol) were stirred in 20 mL of dry DMF at 80 °C for 14 h under a nitrogen atmosphere. After cooling to room temperature, the mixture was diluted with 50 mL of CH₂Cl₂, and the solid was filtered off and washed with CH₂Cl₂ (3 × 10 mL). The filtrate was concentrated to give the crude phthalimide which was used in the next step without further purification. The resulting phthalimide and hydrazine monohydrate (1.0 mL, 20.4 mmol) were mixed in EtOH (50 mL), and the mixture was heated at reflux for 14 h. After cooling to room temperature, the mixture was diluted with 50 mL of CHCl₃, and the solid was filtered off and washed with CH₂Cl₂ (3 × 15 mL). The filtrate was concentrated under vacuum, and the residue was redissolved in CHCl₃ (30 mL). The solution was acidified (pH 2) with 1M HCl aq and diluted with H₂O, and the aqueous layer was washed with EtOAc (3 × 30 mL). The resulting aqueous solution was basified (pH 12) with 1M NaOH aq, and extracted with CH₂Cl₂ (3 × 50 mL). The combined organic layers were dried over Na₂SO₄ and evaporated under vacuum to give the product 3 as a white solid (307 mg, 77%). ¹H NMR (400 MHz, CDCl₃) δ 8.37 (d, J = 7.9 Hz, 1H), 8.31 (d, J = 7.9 Hz, 1H), 8.28 (d, J = 7.8 Hz, 1H), 8.18 (d, J = 7.8 Hz, 1H), 7.84 (t, J = 7.8 Hz, 1H), 7.83 (t, J = 7.8 Hz, 1H), 7.74 (t, J = 7.7 Hz, 1H), 7.67 (t, J = 7.7 Hz, 1H), 7.57 (d, J = 7.7 Hz, 1H), 7.56 (d, J = 7.7 Hz, 1H), 7.24 (d, J = 7.6 Hz, 1H), 7.15 (d, J = 7.6 Hz, 1H), 4.90 (s, 4H), 4.04 (s, 2H), 2.62 (s, 3H). ¹³C NMR (101 MHz, CDCl₃) δ 161.1, 157.9 (two resonance signals), 157.8, 155.8, 155.6, 155.5⁵, 155.5¹, 137.40, 137.42, 137.3, 137.0, 123.2, 121.3, 121.1, 121.1, 119.8, 119.7, 119.2, 118.2, 74.0, 73.9, 47.8, 24.6. HRMS (ESI+, m/z) calculated for C₂₄H₂₄N₅O [M+H]⁺ 398.1975; found 398.1974.