Triphenylphosphine (2.8 g, 10.8 mmol) was dissolved in THF (5 mL) and cooled to 0° C. To this colorless solution diethylazodicarboxylate (1.9 grams, 10.8 mmol) was added dropwise to afford an orange solution. After 15 min at 0° C., a copious precipitate had formed. 4-Hydroxy-naphthalen-1-yl-carbamic acid tert-butyl ester (934 mg, 3.6 mmol) and tetrahydro-4H-pyran-4-ol (552 mg, 5.4 mmol) were then added in one portion as a solution in 2 mL of THF. The purple suspension was stirred at 0° C. for one h then at room temperature for 48 h. The solvent was then evaporated and chromatographed on silica gel (40% EtOAc-hexanes) to provide 680 mg (55%) of [4-(tetrahydro-pyran-4-yloxy)-naphthalen-1-yl]-carbamic acid tert-butyl ester as a purple solid.
