To 3,5-di-tert­-butyl salicylic acid (2.03 g, 8.1 mmol) in a Schlenk vessel was added PPh₃ (8.5 g, 33 mmol) and 2‑aminophenol (0.89 g, 8.1 mmol), and the atmosphere in the vessel was replaced with argon. Acetonitrile (~25 ml), and then triethylamine (4.5 ml, 45 mmol) were added, with stirring. CCl₄ (7.8 ml, 81 mmol) was added dropwise over 4 hours. The mixture was stirred for 48 hours, after which time the solution was filtered, washed through with a little Et₂O, which caused a further precipitation, this precipitate was also removed by filtration. The solvents were removed in vacuo, and the product extracted with hexane (3 × 100 ml). The combined extracts were dried in vacuo, and the pale yellow powder was purified by flash chromatography on a silica column, eluted with hexane-ethyl acetate (50:1), affording HL¹² as a fine white powder (0.30 g, 11%) after removal of solvent.

¹H NMR 400 MHz (CDCl₃): δ ppm 11.95 (s, 1H, OH), 7.92 (d, ⁴J_HH = 2 Hz, 1H, ArH), 7.71 (m, 1H, ArH), 7.62 (m, 1H, ArH), 7.52 (d, ⁴J_HH = 2 Hz, 1H, ArH), 1.50 (s, 9H, C(CH₃)₃), 1.39 (s, 9H, C(CH₃)₃)

¹³C{¹H} NMR 100 MHz (CDCl₃): δ ppm 164.0 (benzoxazole N=C-O), 155.9, 149.1, 141.1, 140.1, 137.2, 128.5, 125.1, 124.6, 121.3, 113.0, 110.6, 109.8 (Ar), 35.3, 34.5 (C(CH₃)₃), 31.5, 29.5 (C(CH₃)₃)

EA: found (calc) C: 78.13 (77.98), H: 7.89 (7.79), 4.33 (4.33)

MS (EI⁺): m/z 323 (M⁺), 308 ([M–CH₃]⁺)

IR (ATR): cm^–1 2959, 2361, 1624 (C=N), 1545, 1454, 1437, 1361, 1247, 1176, 1109, 1089, 953, 886, 868, 804, 776, 758, 743, 700, 668