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Example 5 5-hydroxymethyl-1,4-benzodioxan (5). To a suspension of lithium aluminum hydride (7.0 g, 0.18 mmol) in dry diethyl ether (100 mL) was added a solution of ethyl 1,4-benzodioxan-5-carboxylate (35 g, 0.17 mmol) in diethyl ether (100 mL). After boiling under reflux for 2 h, the reaction mixture was cooled to 0° C. and carefully treated with water (35 mL) and 4N aqueous sodium hydroxide (35 mL). The resulting mixture was filtered and dried (Na2SO4). Evaporation of the solvents afforded 25 g (88percent) crystalline title compound: mp 51-53° C.; 1H NMR (CDCl3) δ 2.50 (s, 1H), 4.20-4.3 (m, 4H), 4.60 (s, 2H), 6.75-6.90 (m, 3H).
Reference：
[1] Patent: US2002/32205, 2002, A1,
2
[ 3943-73-5 ]
[ 1643-19-2 ]
[ 107-06-2 ]
[ 261767-10-6 ]
Yield
Reaction Conditions
Operation in experiment
94%
With hydrogenchloride; sodium chloride; potassium carbonate In water
A mixture of ethyl 2,3-dihydroxybenzoate (1000 g), tetra-n-butyl-ammonium bromide (880 g), potassium carbonate (1552 g), 1,2-dichloroethane (3216 g), and water (10 kg) was refluxed for 5 hours. The solution was cooled and extracted with toluene. The extract was washed with a solution of 1N hydrochloric acid and sodium chloride. The solution was partially concentrated and filtered through silica gel (300 g). The filtrated was concentrated to give the title compound (1074 g, 94percent); m.p. 48-51° C.
Reference：
[1] Patent: US6172062, 2001, B2,
3
[ 4442-53-9 ]
[ 64-17-5 ]
[ 261767-10-6 ]
Reference：
[1] Chemical and Pharmaceutical Bulletin, 2014, vol. 62, # 11, p. 1110 - 1118
[2] Patent: CN103664910, 2017, B, . Location in patent: Paragraph 011
Example 5 5-hydroxymethyl-1,4-benzodioxan (5). To a suspension of lithium aluminum hydride (7.0 g, 0.18 mmol) in dry diethyl ether (100 mL) was added a solution of ethyl 1,4-benzodioxan-5-carboxylate (35 g, 0.17 mmol) in diethyl ether (100 mL). After boiling under reflux for 2 h, the reaction mixture was cooled to 0 C. and carefully treated with water (35 mL) and 4N aqueous sodium hydroxide (35 mL). The resulting mixture was filtered and dried (Na2SO4). Evaporation of the solvents afforded 25 g (88%) crystalline title compound: mp 51-53 C.; 1H NMR (CDCl3) delta 2.50 (s, 1H), 4.20-4.3 (m, 4H), 4.60 (s, 2H), 6.75-6.90 (m, 3H).
With hydrogenchloride; sodium chloride; potassium carbonate; In water;
A mixture of <strong>[3943-73-5]ethyl 2,3-dihydroxybenzoate</strong> (1000 g), tetra-n-butyl-ammonium bromide (880 g), potassium carbonate (1552 g), 1,2-dichloroethane (3216 g), and water (10 kg) was refluxed for 5 hours. The solution was cooled and extracted with toluene. The extract was washed with a solution of 1N hydrochloric acid and sodium chloride. The solution was partially concentrated and filtered through silica gel (300 g). The filtrated was concentrated to give the title compound (1074 g, 94%); m.p. 48-51 C.
General procedure: 2,3-Dihydrobenzo[b]-[1,4] dioxinecarboxylic acid A, B and C (10 mmol) in ethanol (200 mL) was treated with thionyl chloride (5 mL) under reflux overnight. Excess ethanol was distilled out and the solid left was dissolved in ethyl acetate (150 mL), washed with saturation sodium bicarbonate (200 mL) and then sodium chloride (200 mL). After drying the organic layer with anhydrous Na2SO4 and evaporating the solvent under reduced pressure and solid appeared. The solid was recrystallized from ethanol to obtain the compound A1, B1 and C1. The completion of the reaction was monitored on TLC by using silica gel-G coated plates by using ethyl acetate and petroleum ether (1 : 1) as the elution and observed in UV light.
With sulfuric acid; at 80℃; for 10h;
To 50 ml of ethanol was added 10 g of 1,4-benzodioxane-5-carboxylic acid, Slowly drip 3ml concentrated sulfuric acid, reflux at 80°C , the reaction 10h. After completion of the reaction, the solvent was evaporated, 20 ml of ethyl acetate was added, washed three times with saturated sodium chloride, dried over anhydrous sodium sulfate, Flash column chromatography to give colorless transparent oily liquid 1,4-benzodioxane-5-carboxylate.
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