Reaktion #11246

Reaktionsgleichung

potassium carbonate

3-Bromo-2-hydroxy-5-methoxy-benzaldehyde

dimethyl bromomalonate

→

benzofuran

Ausbeute 56.0%

Methyl 7-bromo-5-methoxy-1-benzofuran-2-carboxylate

Ausbeute 56.0%

Lösungsmittel

toluene

Reaktionsbedingungen

Aufarbeitung

1. 1
   TemperaturThe reaction was heated
2. 2
   Temperaturat reflux under a Dean-Stark trap for 48 h
3. 3
   EinengenThe reaction was concentrated
4. 4
   workup.DISSOLUTIONthe residue dissolved with dichloromethane (−0.5 L)
5. 5
   Filtrationfiltered through Celite
6. 6
   Waschenwashing with dichloromethane (˜0.5 L)
7. 7
   WaschenThe filtrate was washed with 1 L of 1M sodium hydroxide and water (2×1 L)
8. 8
   Einengenthe filtrate was concentrated

Vorschrift

To a solution containing 3-Bromo-2-hydroxy-5-methoxy-benzaldehyde (94.7 g, 0.410 mol) and dimethyl bromomalonate (103 g, 0.492 mol) in toluene (1.2 L) was added freshly powdered potassium carbonate (85 g, 0.615 mol) and tetra-n-butylammonium bromide (13.2 g, 0.041 mol). The reaction was heated at reflux under a Dean-Stark trap for 48 h. The reaction was concentrated and the residue dissolved with dichloromethane (−0.5 L) and filtered through Celite, washing with dichloromethane (˜0.5 L). The filtrate was washed with 1 L of 1M sodium hydroxide and water (2×1 L). The organic phase was then passed through a 400 g pad of silica gel washing with dichloromethane (˜1 L) and the filtrate was concentrated to give the desired benzofuran (64 g, 56%) as an orange solid, mp 107–111° C. 1H NMR δ (CDCl3) 7.50 (s, 1H), 7.23 (d, 1H), 7.03 (d, 1H), 3.98 (s, 3H), 3.82 (s, 3H).

Quelle