Reaktion #2076

Reaktionsgleichung

methanesulfonic acid

sodium methoxide

2-(3-hydroxyphenyl)-3-methylbenzofuran

Glycidol

→

2-[3-(2,3-dihydroxypropoxy)phenyl]-3-methylbenzofuran

Lösungsmittel

methanol

Reaktionsbedingungen

Aufarbeitung

1. 1
   Temperaturthe system is gradually heated
2. 2
   Temperaturat reflux for 18 hours
3. 3
   SonstigeThe solvent is removed by rotary evaporation
4. 4
   Sonstigeto remove any 3-methoxy-1,2-propanediol by-product

Vorschrift

The ester which results from the condensation of 2'-hydroxyacetophenone and m-anisic acid is converted to 2-(3-methoxyphenyl)-3-methylbenzofuran by reductive cyclization in dioxane with a titanium tetrachloride/zinc metal catalyst according to the method of Banerji and Nayak, J. Chem. Soc., Chem. Comm., (1990), 150. The 2-(3-methoxyphenyl)-3-methylbenzofuran (47.6 gm, 0.198 mol) is treated with several volumes of pyridine hydrochloride at 200° C. for about 6 hours to cleave the methyl ether moiety to the free hydroxyl group. Three volumes of water are added to the cooled reaction mixture and the system is extracted twice with ether. The ether extracts are combined, washed once with water and then dried over sodium sulfate. Removal of solvent by rotary evaporation affords the desired product, 2-(3-hydroxyphenyl)-3-methylbenzofuran. 2-(3-hydroxyphenyl)-3-methylbenzofuran (22.4 gm 0.1 mol) is dissolved in 100 mL of methanol in a 250 ml round bottom flask under an atmosphere of argon. To this well stirred solution is added sodium methoxide (0.54 gm, 0.01 mol). Glycidol (Aldrich, 8.14 gm, 0.11 mol) is added and the system is gradually heated and held at reflux for 18 hours. The solution is neutralized with methanesulfonic acid. The solvent is removed by rotary evaporation. The resulting product is heated on a Kugelrohr apparatus at 200° C. under a vacuum of 1 mm Hg, to remove any 3-methoxy-1,2-propanediol by-product, affording 2-[3-(2,3-dihydroxypropoxy)phenyl]-3-methylbenzofuran having the structure: ##STR55##

Quelle