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With potassium carbonate; In N,N-dimethyl-formamide; at 20℃; for 48h;
Potassium carbonate (9.42 mmol) and iodomethane (8.45 mmol) were added to a solution of crude <strong>[57764-50-8]ethyl 6-hydroxybenzo[d]isoxazole-3-carboxylate</strong> (2.42 mmol) in N,N-dimethylformamide (30 mL) and the reaction mixture was maintained for 48 h at rt in the dark. The reaction mixture was diluted with water (100 mL) and was extracted with ethyl acetate (2*100 mL). The combined organic layers were washed with brine (3*100 mL), dried (magnesium sulfate), and concentrated. The residue was purified by chromatography (30/1 petroleum ether/ethyl acetate) to provide ethyl 6-methoxybenzo[d]isoxazole-3-carboxylate in 19% yield as a yellow solid. The following ester was prepared using this method: Ethyl 6-methoxybenzo[d]isoxazole-3-carboxylate.
With caesium carbonate;sodium iodide; In acetone; at 20 - 56℃; for 7h;
Step 1.1 : e-Benzyloxy-benzordlisoxazole-S-carboxylic acid ethyl ester; To a solution of 0.98 g (4.73 mMol) <strong>[57764-50-8]6-hydroxy-benzo[d]isoxazole-3-carboxylic acid ethyl ester</strong>[preparation see: J. Am. Chem. Soc. 97 (1974), 7305] in 100 ml acetone, 545 mul (4.73 mMol) benzylchloride, 3.08 g (9.46 mMol) Cs2CO3 und 10 mg NaI are added. Then the mixture is stirred for 2 h at rt and 5 h at 56 C. The reaction mixture is diluted with EtOAc and water, the aq. phase separated off and extracted with EtOAc. The organic layers are washed with water and brine, dried (Na2SO4) and concentrated after addition of 10 g SiO2. The resulting powder is put on top of a chromatography column (SiO2) and the title compound eluated with hexan/EtOAc 9:1 ? 8:2 ? 7:3: MS: [M+1]+ = 298; TLC(hexane/EtOAc 3:1 ): Rf = 0.54.
With 1H-imidazole; In N,N-dimethyl-formamide; at 20℃; for 0.833333h;
Step 1.1 *: theta-Triisopropylsilanyloxy-benzordiisoxazole-S-carboxylic acid ethyl ester; To a solution of 0.80 g (3.86 mMol) <strong>[57764-50-8]6-hydroxy-benzo[d]isoxazole-3-carboxylic acid ethyl ester</strong>[preparation see: J. Am. Chem. Soc. 97 (1974), 7305] in 8 ml DMF, 1.16 g (17 mMol) imidazol and 2.15 ml chlortriisopropylsilane (95 %; 9.7 mMol) are added. After 50 min, the mixture is poured into ice-water and extracted twice with EtOAc. The organic phases are washed with 10 % citric acid solution, 2x water and brine, dried (Na2SO4) and concentrated.Column chromatography (SiO2; hexane/EtOAc 29:1 ) gives the title compound: MS: [M+1]+ =364; TLC(hexane/EtOAc 9:1 ): Rf = 0.5.
With potassium phosphate; In 1-methyl-pyrrolidin-2-one; at 20℃; for 22h;
Step 4.1 : 6-(2-Chloro-pyrimidin-4-yloxy)-benzordlisoxazole-3-carboxylic acid ethyl ester; A suspension of 2.7 g (18.1 mMol) 2,4-dichloropyrimidine, 4.12 g (19.9 mMol) 6-hydroxy- benzo[d]isoxazole-3-carboxylic acid ethyl ester [preparation see: J. Am. Chem. Soc. 97 (1974), 7305] and 8.45 g (39.8 mMol) K3PO4 in 90 ml NMP is stirred for 22 h at rt. Then the mixture is diluted with 0.5 I CH2CI2 and 0.9 I of a 5 % citric acid solution. The organic phase is separated off, washed with water and brine, dried (Na2SO4) and concentrated. Column chromatography (SiO2; CH2CI2) gives the title compound: MS: [M+1]+ = 320; TLC(CH2CI2/Et0Ac 49:1 ): Rf = 0.42.
6-amino-benz[<i>d</i>]isoxazole-3-carboxylic acid ethyl ester[ No CAS ]
[ 57764-50-8 ]
Yield
Reaction Conditions
Operation in experiment
99%
Ethyl 6-aminobenzo[d]isoxazole-3-carboxylate (2.43 mmol) was diluted with a solution of sulfuric acid (2.5 mL) in water (2.5 mL) and the resulting mixture was maintained at rt for 30 min. A solution of sodium nitrite (2.67 mmol) in water (2.5 ml) was added dropwise at 0 C. and the resulting mixture was maintained for 30 min at 0 C. This aqueous solution was added to a cold (0 C.) solution of copper (II) nitrate (149 mmol) in water (80 mL) and the reaction mixture was allowed to warm to rt. After 5 min., copper (I) oxide (2.78 mmol) was added to the mixture and the reaction mixture was maintained for 1 h at rt. The reaction mixture was extracted with ethyl acetate (3*100 mL) and the combined organic layers were dried (magnesium sulfate) and concentrated to provide crude ethyl 6-hydroxybenzo[d]isoxazole-3-carboxylate in 99% yield as a brown oil.
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