Hydrochloric Acid → 2-Naphthol

Participants

Reaction Steps

Acrylic acid (1.36 mL, 20.0 mmol) was added to a solution in which 2-naphthol (1.44 g, 10.0 mmol) and AMBERLIST (produced by Aldrich, strong acid, 1.0 g) serving as an ion-exchange resin were dissolved into toluene (30 mL), while the solution was agitated. The resulting mixed solution was refluxed for a day. The resulting suspension was filtrated through celite, and the solvent was removed by distillation in a vacuum. The residue was refined by silica gel flash chromatography (dissolution medium hexane-EtOAc=20:1 (v/v)) to obtain a pyran derivative (1.78 g, 9.0 mmol, yield 90%). A solution in which the resulting pyran derivative (1.78 g, 9.0 mmol) was dissolved into THF (40 mL) was blended with 1-N LiOH (30 mL) and the resulting reaction mixed solution was agitated at room temperature for 6 hours. The resulting reaction mixed solution was poured into 1-N HCl (100 mL), extraction with EtOAc was performed two times, and washing was performed with a saline solution. Organic layers were mixed and dried with anhydrous Na2SO4. The solvent was removed by distillation in a vacuum. The residue was refined by silica gel flash chromatography (dissolution medium hexane-EtOAc=4:1 to 1:1 (v/v)) to obtain 2-Naphthol compound S2, that is, 3-(2-hydroxynaphthalen-1-yl)propanoic acid (4.05 g, 18.7 mmol) at a yield of 62%. The spectrum data thereof are as described below. In this regard, various 2-naphthol compounds used as starting materials in examples described later were synthesized by this method.

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