Cesium carbonate → Ethyl alpha-(4-carbomethoxy-2-n-propylphenoxy)-3,4-methylenedioxyphenylacetate

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Reaction Steps

To a 2 L three necked 24/40 round bottom flask equipped with a mechanical stirrer, a nitrogen inlet and a dropping funnel was first added a solution of 36.0 g (0.185 mol) of methyl 4-hydroxy-3-n-propylbenzoate dissolved in 700 mL of anhydrous DMF followed by 66.4 g (0.204 mol) of cesium carbonate. The flask was purged with nitrogen and the reaction mixture was stirred at room temperature for 2 hours. A solution of 58.5 g (0.204 mol) of ethyl α-bromo-3,4-methylenedioxyphenylacetate dissolved in 100 mL of DMF was then added via an addition funnel over a 15 minute period. The reaction mixture was stirred an additional 1 hour at room temperature then quenched by addition to 5 L of a 5% aqueous citric acid solution. The organic product was extracted into diethylether (2×4 L), the organic layers were separated, washed with saturated aqueous NaCl, dried (MgSO4), filtered, and evaporated. The residue was applied to a silica gel (2 kg; 70-230 mesh) column equilibrated in 10% CH2Cl2 -hexane. The column was then eluted successively with 12 L of 10% CH2Cl2 -hexane, 12 L of 5% EtOAc-hexane, 4 L of 7.5% EtOAc-hexane, 12 L of 10% EtOAc-hexane, and finally 8 L of 20% EtOAc-hexane. Combination of the purified fractions and evaporation in vacuo afforded 76.3 g (74.2 theoretical) of the title compound as a pale yellow oil which was used without further purification in the next step.

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