Reaktion #313286

Reaktionsgleichung

HCl

oxalyl chloride

3-Bromo-2-methyl-benzo[b]thiophene-7-carboxylic acid methyl ester

NaOH

N,O-dimethyl hydroxylamine hydrochloride

Et3N

→

title compound

Ausbeute 79.8%

3-Bromo-2-methyl-benzo[b]thiophene-7-carboxylic Acid methoxy-methyl-amide

Ausbeute 79.8%

Lösungsmittel

H2O

CH2Cl2

CH2Cl2

Reaktionsbedingungen

Aufarbeitung

1. 1
   TemperaturIt is refluxed for 4 h
2. 2
   FiltrationThe resulting precipitate is collected by filtration
3. 3
   Waschenwashed with H2O (50 mL)
4. 4
   Sonstigedried in a vac-oven
5. 5
   SonstigeThe material obtained
6. 6
   workup.WAITat rt for 4 h
7. 7
   SonstigeThe excess reagent and solvent are removed in vacuo
8. 8
   Sonstigethe resulting reaction mixture
9. 9
   workup.STIRRINGis stirred at rt for 2 h
10. 10
    Waschenwashed with 0.1 M HCl (3×300 mL)
11. 11
    Trocknendried with Na2SO4
12. 12
    Filtrationfiltered
13. 13
    Einengenconcentrated
14. 14
    SonstigePurification of the crude material by chromatography

Vorschrift

3-Bromo-2-methyl-benzo[b]thiophene-7-carboxylic acid methyl ester 7.82 g, 27.43 mmol) was treated with NaOH (5 M, 28 mL, 140 mmol) and H2O (100 mL). It is refluxed for 4 h; cooled to 0° C., and acidified to pH (3-4) using 5 M HCl. The resulting precipitate is collected by filtration, washed with H2O (50 mL), and dried in a vac-oven. The material obtained is then treated with oxalyl chloride (2M, 27 mL) with a few drops of DMF. The reaction is stirred at 0° C. for 10 min, and at rt for 4 h. The excess reagent and solvent are removed in vacuo. The residue is finally treated with N,O-dimethyl hydroxylamine hydrochloride (4.00 g, 41.14 mmol) and Et3N (9.6 mL, 68.58 mmol) and CH2Cl2 (200 mL), and the resulting reaction mixture is stirred at rt for 2 h. It is diluted with CH2Cl2 (200 mL), washed with 0.1 M HCl (3×300 mL); dried with Na2SO4, filtered and concentrated. Purification of the crude material by chromatography gives the title compound (6.87 g, 21.89 mmol, 53%). 1H NMR (CDCl3): δ. 2.56 (s, 3H), 3.42 (s, 3H), 3.59 (s, 3H), 7.45 (t, J=7.9 Hz, 2H), 7.81-7.87 (m, 1H) ppm. ES-MS (m/z): calcd for C12H12BrNO2S (M)+: 314.1. found: 314.2.

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