General procedure for the synthesis of (3aR,4S,7R,7aS)-rel-hexahydro-4,7-methanoisobenzofuran-1,3-dione from cis-5-norbornene-exo-2,3-dicarboxylic anhydride: 200 g of cis-5-norbornene-exo-2,3-dicarboxylic anhydride (from step 2) was mixed with 1.5 L of toluene, heated until completely dissolved, and then transferred to a 4-L high pressure reactor. 10 g of Pd/Pt catalyst was added to the reactor and the system was purged under 10 bar hydrogen pressure for 5 minutes. After purging, the hydrogen pressure was adjusted to 12 bar and the hydrogenation reaction was carried out at 160°C and 20 bar hydrogen pressure. After the reaction lasted 70 minutes, the catalyst was removed. The reaction mixture was transferred to 5 L of hexane and after filtration and drying, 182 g of white solid product (compound 4) was obtained. The structure of the product was confirmed by NMR (1H and 13C NMR, JEOL JNM-LA400) and IR spectroscopy (AVATAR 360FT-IR). The relevant spectral data are displayed in Figures 1, 2, 4 and 5, respectively.
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