Water → 5-Methoxy-2-tetralone

関与物質

反応条件

反応手順

1,6-Dihydroxynaphthalene (44 g (0.247 mole)) was mixed with 245 mL of 2N NaOH and 55 mL of methyl sulfate. The mixture was stirred at room temperature. When the pH of the mixture was 6, 124 mL of 2N NaOH and 26.4 mL of methyl sulfate were added and stirred until 1,6-dihydroxynaphthalene was disappeared. Excess of methyl sulfate was destroyed by heating for 30 minutes at 100° C. The warm liquid was acidified and extracted with CH2Cl2. The CH2Cl2 layer was washed twice with 2N NaOH and evaporated. A yield of 47.73 g (92%) of 1,6-dimethoxynaphthanene was obtained. Sodium (19 g) was added to a solution of 22.5 of crude 1,6-dimethoxynaphthalene in 190 mL of boiling ethanol. Ethanol (40 mL) was then added and heating continued under reflux until the Na had disappeared (about 40 minutes). Water (60 mL) was added cautiously and then most of the ethanol was removed under reduced pressure. The residue was mixed with 30 mL of water and the lower aqueous layer was separated and extracted twice with dioxane, which was then combined with the oily upper layer. Water (25 mL) and then hydrochloric acid (density of 1.18 g/mL) until the mixture was acidic (pH 2-3). Then, 3 mL more of HCl was added and the liquid was stirred at about 70° C. for 30 minutes. The lower oily layer was separated, the aqueous layer was diluted with 100 mL of water, separated from more oil, and extracted thrice with methylene chloride. The combined oil and methylene chloride extracts were stirred with 50 mL of saturated aqueous sodium bisulfite until crystallization began. The solid was triturated with ether, then washed with ether and dried. Free 5-methoxy-2-tetralone was obtained by treating the bisulfite addition compound with excess 10% Na2CO3 and extracting the resulting mixture with methylene chloride. The extract was washed with 10% HCl and then with water and dried with Na2SO4. Volatiles were removed under reduced pressure to leave 17 g (81% yield) of liquid. On keeping, the 3,4-Dihydro-5-methoxy-2-(1H)-naphthalenone (hereinafter, "Compound 20") solidified in massive prisms with a melting point of 25°-36° C.

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