Reaktion #2319529

Reaktionsgleichung

acetic acid

5-aminobenzo[b]thiophene

formaldehyde

acetic acid

sodium cyanoborohydride

→

5-(dimethyl)aminobenzo[b]thiophene

Ausbeute 88.0%

Lösungsmittel

CH3CN

ether

Reaktionsbedingungen

Aufarbeitung

1. 1
   SonstigeThe ethereal layer was separated
2. 2
   Waschenwashed with 1M KOH (3×)
3. 3
   Trocknenwith saturated NaCl solution, dried over anhydrous Na2SO4
4. 4
   Sonstigeevaporated to dryness in vacuo
5. 5
   SonstigeThe residual dark oily solid was purified by chromatography on 800 ml of silica gel
6. 6
   WaschenElution with 97 hexane

Vorschrift

To a stirred solution of 5-aminobenzo[b]thiophene (4.55 g, 0.03 mole) in CH3CN (175 ml) was added 37% aqueous formaldehyde (28 ml, 0.035 mole) followed by sodium cyanoborohydride (6.65 g, 0.105 mole). Glacial acetic acid (3.5 ml) was added in small increments over 15 minutes. After 1 hour, another 3.5 ml of acetic acid was added and after another 1 hour, the mixture was poured into ether (700 ml). The ethereal layer was separated, washed with 1M KOH (3×) then with saturated NaCl solution, dried over anhydrous Na2SO4, and evaporated to dryness in vacuo. The residual dark oily solid was purified by chromatography on 800 ml of silica gel. Elution with 97 hexane: 3 ethyl acetate afforded 4.6 g (88%) of 5-(dimethyl)aminobenzo[b]thiophene as a light yellow solid, m.p. 52°-54° C.

Quelle