5-Chlorocarbonylphthalide → 1-Oxo-1,3-dihydroisobenzofuran-5-carbaldehyde

Participants

Reaction Steps

In a hydrogenator a mixture of 7 g (0.036 mole) of 5-chlorocarbonylphthalide, 50 ml of toluene, 0.1 ml of the quinoline/sulfur mixture and 0.7 g of previously reduced 5% Pd/BaSO4 is charged. The mixture is hydrogenated at 80° C. under 3.5 bar for 7 hours. At this point the reaction no longer proceeds because of the co-precipitation of the formed product Thus, it is stopped and the mixture is filtered in the warm in order to put the product. into solution again. A second amount of 0.7 g of 5% Pd/BaSO4 is added to the filtrate and the hydrogenation starts again under the above described conditions. After 15 minutes, no more absorption of hydrogen is observed. Hydrogenation is stopped and the catalyst is filtered off in the warm. After cooling, the solution is concentrated under vacuum to a residue which is taken up with ethyl acetate. The organic phase is washed with a 5% aqueous solution of NaHCO3, concentrated to a little volume and the separated product is filter. There is obtained 4.2 g of 5-formylphthalide with a purity (HPLC)=42% (yield 30%).

Provenance & Evidence