Reaktion #1151

Reaktionsgleichung

ethyl acetate

Boron tribromide

methyl 6-methoxybenzofuran-2-carboxylate

→

methyl 6-hydroxybenzofuran-2-carboxylate

Ausbeute 73.0%

Lösungsmittel

dichloromethane

Reaktionsbedingungen

Aufarbeitung

1. 1
   WaschenAfter the organic layer was washed with water
2. 2
   Trocknendried (MgSO4)
3. 3
   workup.DISTILLATIONthe solvent was distilled off
4. 4
   workup.ADDITION10% hydrochloric acid-methanol (60 ml) was added to the residue
5. 5
   Temperaturby heating at 70° to 80° C. for 5 hours
6. 6
   EinengenThe reaction mixture was concentrated under reduced pressure
7. 7
   Filtrationthe resulting crystals of methyl 6-hydroxybenzofuran-2-carboxylate (10.75 g) were collected by filtration
8. 8
   EinengenThe filtrate was concentrated
9. 9
   WaschenFrom the fraction eluted with diethyl ether-hexane (1:2

Vorschrift

Boron tribromide (24.9 g) was added dropwise to a solution of methyl 6-methoxybenzofuran-2-carboxylate (18.6 g) in dichloromethane (200 ml) at 0° C., followed by stirring at room temperature for 1 day. The reaction mixture was poured over ice water; ethyl acetate (300 ml) was added. After the organic layer was washed with water and dried (MgSO4), the solvent was distilled off; 10% hydrochloric acid-methanol (60 ml) was added to the residue, followed by heating at 70° to 80° C. for 5 hours. The reaction mixture was concentrated under reduced pressure; the resulting crystals of methyl 6-hydroxybenzofuran-2-carboxylate (10.75 g) were collected by filtration using diethyl ether-isopropyl ether (2:1, v/v). The filtrate was concentrated; the residue was subjected to silica gel column chromatography. From the fraction eluted with diethyl ether-hexane (1:2, v/v), methyl 6-hydroxybenzofuran-2-carboxylate (1.75 g) was obtained (total yield 73%), which was then recrystallized from diethyl ether-isopropyl ether to yield colorless prisms having a melting point of 176° to 177° C.

Quelle