Reaktion #306007

Reaktionsgleichung

2-t-butyldimethylsilyl-3-(t-butyldimethylsilyloxymethylene)-6-methoxy -7-isopropoxybenzofuran

hydrochloric acid

→

title compound

Ausbeute 53.7%

2-t-Butyldimethylsilyl-3-formyl-6-methoxy-7-isopropoxybenzofuran

Ausbeute 53.7%

Lösungsmittel

methanol

Reaktionsbedingungen

Aufarbeitung

1. 1
   Sonstigequenched with triethylamine (2 mL)
2. 2
   Sonstigethe solvent removed by distillation under vacuum
3. 3
   workup.DISSOLUTIONThe residue was dissolved in dichloromethane (20 mL)
4. 4
   Waschenwashed with water (10 mL)
5. 5
   Trocknendried over magnesium sulfate
6. 6
   Einengenconcentrated under vacuum and co-distilled with toluene (20 mL)
7. 7
   workup.DISSOLUTIONThe crude product was dissolved in dry dichloromethane (4 mL)
8. 8
   workup.ADDITIONadded to a stirred solution of Collin's reagent (chromium trioxide (1.01 g), pyridine (1.65 mL) in dry dichloromethane (30 mL))
9. 9
   workup.STIRRINGThe suspension was stirred for 10 minutes
10. 10
    Filtrationfiltered
11. 11
    Waschenthe residue washed with diethyl ether (20 mL)
12. 12
    EinengenThe filtrate was concentrated onto silica (10 g)
13. 13
    Sonstigepurified by flash chromatography (silica gel, eluent=hexane/diethyl-ether/triethylamine (90:9:1)

Vorschrift

To a solution of 2-t-butyldimethylsilyl-3-(t-butyldimethylsilyloxymethylene)-6-methoxy -7-isopropoxybenzofuran (2.69 mmol) in methanol (100 mL) was added concentrated hydrochloric acid (200 μL) and the reaction was stirred for 30 minutes (monitored by tic), quenched with triethylamine (2 mL) and the solvent removed by distillation under vacuum. The residue was dissolved in dichloromethane (20 mL), washed with water (10 mL), dried over magnesium sulfate, concentrated under vacuum and co-distilled with toluene (20 mL). The crude product was dissolved in dry dichloromethane (4 mL) and added to a stirred solution of Collin's reagent (chromium trioxide (1.01 g), pyridine (1.65 mL) in dry dichloromethane (30 mL)). The suspension was stirred for 10 minutes, filtered and the residue washed with diethyl ether (20 mL). The filtrate was concentrated onto silica (10 g) and purified by flash chromatography (silica gel, eluent=hexane/diethyl-ether/triethylamine (90:9:1) to afford the title compound as a light yellow oil (503 mg, 48%); 1H NMR (300 MHz, CDCl3) δ 10.25(s, 1H, CHO), 7.79(d, 1H, J=8.45 Hz), 6.98(d, 1H, J=8.46 Hz), 4.65(m, 1H), 3.89(s, 3H, OMe), 1.35(d, 6H, J=6.17 Hz), 0.97(s, 9H), 0.45(s, 6H).

Quelle