Reaktion #2348123

Reaktionsgleichung

methyl 5-bromosalicylate

Ac2O

Et3N

→

methyl 2-acetoxy-5-bromobenzoate

Ausbeute 99.8%

Lösungsmittel

water

Reaktionsbedingungen

Aufarbeitung

1. 1
   SonstigeIn a 50 mL round-bottomed flask fitted with condenser and magnetic stirrer
2. 2
   Extraktionextracted with ethyl acetate
3. 3
   WaschenThe organic layer was washed with water
4. 4
   Sonstigedried
5. 5
   Einengenconcentrated

Vorschrift

In a 50 mL round-bottomed flask fitted with condenser and magnetic stirrer were placed methyl 5-bromosalicylate (5.0 g, 21.64 mmol), Ac2O (2.65 g, 25.97 mmol), Et3N (2.63 g, 25.97 mmol) and catalytic amount of DMAP. The reaction mixture was stirred for 24 h at room temperature. The reaction mixture was poured into water and extracted with ethyl acetate. The organic layer was washed with water, dried and concentrated to give methyl 2-acetoxy-5-bromobenzoate (5.9 g, 98%). To a stirred solution of methyl 2-acetoxy-5-bromobenzoate (5.9 g, 21.61 mmol) in acetonitrile (80 mL) were added 4-acetoxystyrene (3.68 g, 22.69 mmol), N,N-diisopropylethylamine (8.38 g, 64.82 mmol), biphenyl-2-yl-di-t-butyl phosphine (368 mg, 1.29 mmol) and palladium acetate (291 mg, 1.29 mmol) under N2. The reaction mixture was heated to 80° C. for 48 h and then cooled to room temperature. Water was added and the mixture was extracted with ethyl acetate. The organic layer was separated, washed with water, brine, dried and concentrated to give crude product, which was purified by column chromatography, using 20% ethyl acetate in hexane to give (3.19 g, 42%) of the di-acetoxy stilibene. To a solution of the di-acetoxy stillbene (500 mg, 1.41 mmol) in acetonitrile: THF (10 mL: 10 mL), NaOH (388 mg, 8.47 mmol) was added and stirred for 24 h at room temperature. The reaction mixture was neutralized by dilute HCl and extracted with ethyl acetate. The combined organic layers were washed with water, brine, dried and concentrated to give a crude product, which was purified by crystallization in ethyl acetate and hexane to give 2-hydroxy-5-[(E)-2-(4-hydroxyphenyl)vinyl]benzoic acid (250 mg, 69%). MS (ES) m/z: 256.06 (M), 255.05 (M−1); 13C-NMR (CD3OD): δ 172.3, 161.1, 157.1, 132.7, 129.6, 129.3, 128.0, 127.5, 127.1, 124.3, 117.4, 115.3, 112.7. Mp. 241-243° C.

Quelle