Compound 7

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

Under an inert N₂ atmosphere, a flask was charged with triphosgene (180 mg, 0.61 mmol) and anhydrous toluene (6 mL). A solution of triamine 6 (50 mg, 0.20 mmol) in anhydrous toluene (6 mL) was added dropwise and the reaction mixture was heated to reflux then stirred for 2 hours. The mixture was cooled and the solvent removed under vacuum. The crude solid was triturated with cold toluene, filtered and the filtrate dried under high vacuum to afford tris-isocyanate 7 (63 mg, 0.20 mmol, 91%) as a colourless oil that crystallised over time. ¹H NMR: (400 MHz, (CDCl₃): 1.26 (t, J = 7.6 Hz, 9H, C(1)H), 2.84 (q, J = 7.6 Hz, 6H, C(2)H), 4.50 (s, 6H, C(5)H₂); ¹³C NMR: (100 MHz, (CDCl₃): δ 16.1 (C(1)H₂), 22.8 (C(2)H), 40.4 (C(5)H), 123.1 (C6), 132.4 (C3), 143.1 (C4); ν _max 2973, 2933, 2875, 2243, 1495, 1453, 1335, 1042, 856, 577 cm^-1; HRMS: (ESI⁺) calculated for C₁₈H₂₁N₃O₃Na⁺: 350.1475, found [M+Na]⁺: 350.1474.