Tetrahydro-2-furancarbonyl chloride → N-Phenyl-2-furancarboxamide

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To a stirred solution of N,N'-bis[2,3-bis(acetyloxy)propyl]-5-amino-2,4,6-triiodo-1,3-benzenedicarboxamide (8.73 g, 10 mmol) (prepared as described in EP 431,838) in N,N-dimethylacetamide (30 mL), was added in drops tetrahydrofuran-2-carbonyl chloride (1.8 g, 13 mmol) (prepared as in part A of Example 3) at 0°-5°. After the addition, the mixture was stirred at 0°-5° for 0.5 hour, then at room temperature for 20 hours. Nitrogen gas was purged through the solution for 0.25 hour, and the N,N-dimethylacetamide was removed in vacuo at 40°. The residue was dissolved in ethyl acetate (200 mL), and the solution was washed successively with cold aqueous sodium bicarbonate (2×50 mL), water (2×50 mL) and saturated sodium chloride (2×50 mL). After drying over sodium sulfate, the solvent was removed in vacuo to obtain the title B furanilide as an off-white foamy material (9.27 g, crude). The crude product (7.2 g), upon purification by column chromatography over silica gel (mobile phase: hexane/ethyl acetate) furnished N,N'-bis [2,3-bis (acetyloxy)propyl]-2,4,6-triiodo-5-[[(tetrahydro -2-furanyl) carbonyl]amino]-1,3 -benzenedicarboxamide (6.19 g) , m.p. 101°-104°.

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