Tetrahydrofuran → 4-Methoxyphenol

12.08 g of 4-arm PEG 15 k (Mn=14861 g/mol, 3.3 meq OH) were dissolved in 150 ml of dry tetrahydrofuran under an Ar atmosphere. The solution was dried by refluxing the solvent over molecular sieves until the water content had fallen below 100 ppm, after which it was allowed to cool down to room temperature. 0.78 g of triethylamine (7.7 mmol) were added and a solution of 0.69 g of acryloylchloride (7.7 mmol) in 20 ml of dry dichloromethane was added drop wise at such a rate that the temperature of the reaction mixture remained below 30° C. The resulting suspension was filtered through ca. 1 cm of Celite 545, yielding a pale yellow, clear solution to which 44 mg of MEHQ were added. The solvent was removed by rotary evaporation, the resulting solid was redissolved in 150 ml of water and NaHCO3 was added until pH 8. The aqueous solution was washed twice with 40 ml of diethyl ether, 10 g of NaCl were added and the product was extracted with four 50 ml portions of dichloromethane. The combined organic layers were dried with Na2SO4 and filtered. To the resulting pale yellow solution 30 mg of MEHQ were added and it was concentrated to ca. 35 ml by rotary evaporation. Precipitation in 0.8 l of cold diethyl ether and subsequent filtration and drying at 60° C. in a vacuum oven yielded 11.5 g (94%) of a white powder. The structure of the product was confirmed by 1H NMR, which showed a degree of functionalization of ca. 97%.