methyl 6-hydroxybenzofuran-3-carboxylate synthesis

Yield:-

Reaction Conditions:

with tetrabutyl ammonium fluoride;water in N,N-dimethyl-formamide at 20; for 0.5 h;

Steps:

9.4

Step 9.4: θ-Hvdroxy-benzofuran-S-carboxylic acid methyl ester; 17.9 g (51.4 mMol) δ-Triisopropylsilanyloxy-benzofuran-S-carboxylic acid methyl ester are dissolved in 200 ml DMF. Then 34 g (108 mMol) tetrabutylammoniumfluorid trihydrate are added. After 30 min, the mixture is poured into 400 ml EtOAc and 600 ml water, the aq. phase is separated off and extracted 3 times with EtOAc. The organic layers are washed 4 times with water, brine and dried (Na₂SO₄). Then char coal is added and the mixture filtered. Partial concentration of the filtrate gives the crystalline title compound, which is filtered off and washed with ether and hexane: m.p.: 200-201 °C. More product can be isolated from the filtrate by addition of 280 g SiO₂, concentration, application to a chromatography column (SiO₂; hexane/EtOAc 3: 1 ) and eluation with hexane/EtOAc 3:1.

References:

WO2008/9487,2008,A1 Location in patent:Page/Page column 61