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Diethylazodicarboxylate (22.7 g, 130 mmol) was added over 3 min to a stirred solution of dimethyl 5-hydroxyisophthalate (21 g, 100 mmol), hexaethylene glycol (32 g, 113 mmol) and triphenylphosphine (34 g, 130 mmol) in 250 mL of anhydrous THF. After 2 h the reaction was concentrated and the residue suspended in 200 mL of ethyl ether. After being cooled at 0° C. for 30 min the precipitated triphenylphosphine oxide was removed by filtration and filtrate concentrated. The resultant mixture was chromatographed on silica eluting, first, with ethyl acetate to separate Ph3PO and symmetrical bis-substituted hexaethylene glycol by-product and, second, with 5% MeOH in ethyl acetate to elute desired mono-substituted hexaethylene glycol derivative. Evaporation of the solvent and drying under high vacuum afforded 14.8 g (31%) of the title compound as viscous oil. 1H NMR (DMSO-d6) δ 8.08 (s, 1H), 7.70 (s, 2H), 4.58 (t, J=5.5 Hz, 1H), 4.25 (m, 2H), 3.90 (s, 6H), 3.76 (m, 2H), 3.60 (m, 2H), 3.51 (m, 16H), 3.40 (m, 2H).

1. concentrationAfter 2 h the reaction was concentrated
2. customwas removed by filtration and filtrate
3. concentrationconcentrated
4. customThe resultant mixture was chromatographed on silica eluting
5. customfirst, with ethyl acetate to separate Ph3PO and symmetrical bis-substituted hexaethylene glycol by-product
6. washsecond, with 5% MeOH in ethyl acetate to elute desired mono-substituted hexaethylene glycol derivative
7. customEvaporation of the solvent
8. customdrying under high vacuum