7-Hydroxy-2-naphthalenesulfonic acid → Sodium

Participants

Reaction Steps

A 60% dispersion of sodium hydride (0.37 g, 9.22 mmol) in mineral oil is washed with hexanes twice and suspended in 40 mL of DMF. To this mixture is added slowly via an addition funnel 7-hydroxynaphthalene-2-sulfonic acid, sodium salt (1.25 g, 5.08 mmol) in 25 mL of DMF at room temperature. The reaction mixture is stirred for 2 hours during which time mild bubbling is observed (H2 evolution). The mixture is treated with benzyl bromide (1.5 mL, 12.6 mmol) and stirred for 18 hours at room temperature. Ice is added to decompose the excess NaH and the resultant mixture is concentrated in vacuo. The residue is suspended in acetone and concentrated in vacuo two times and then is dried under high vacuum. The solid is suspended in acetone, filtered and dried to yield the crude 7-benzyloxynaphthalene-2-sulfonic acid, sodium salt as a beige solid. A mixture of the sulfonic acid, sodium salt (2.47 g) in 8 mL of thionyl chloride is heated at 80° C. for 4 hours. A drop of DMF is added with vigorous bubbling resulting and the mixture is heated for an additional 30 minutes. The mixture is allowed to cool to room temperature and concentrated in vacuo. The residue is diluted in EtOAc and washed successively with water (2×), saturated NaHCO3 solution and saturated NaCl. The organic layer is dried over anhydrous MgSO4, filtered and concentrated to yield the title compound as a beige solid (1.26 g, 3.78 mmol). The crude product is of sufficient purity to be used in subsequent reactions.

Provenance & Evidence