Potassium Carbonate → N,N'-Bis[2-(acetyloxy)-1-[(acetyloxy)methyl]ethyl]-5-(3-bromo-2-oxo-1-piperidinyl)-2,4,6-triiodo-1,3-benzenedicarboxamide

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Reaction Steps

To a solution of N,N'-bis[2-(acetyloxy)-1-[(acetyloxy)methyl]ethyl]-5-[(2,5-dibromo-1-oxopentyl)amino]-2,4,6-triiodo-1,3-benzenedicarboxamide of example 9a (32.5 g, 29.1 mmol) in dimethylacetamide (250 ml), was added powdered potassium carbonate (25.2 g, 116.5 mmol). After stirring for 4 hours, the mixture was filtered. The filtrate was freed of the solvent in vacuo at 45° C. and the resulting solid was redissolved in ethyl acetate (500 ml). The ethyl acetate solution was washed with water (2×50 ml) and saturated aqueous sodium chloride (1×100 ml), and dried over anhydrous magnesium sulfate. The solvent was removed in vacuo to obtain a white solid (29.5 g) which, upon crystallization from ethyl acetate (1.2 L), furnished analytically pure N,N'-bis[2-acetyloxy )-1-[(acetyloxy)-methyl]ethyl]-5-(3-bromo-2-oxo-1-piperidinyl)-2,4,6-triiodo-1,3-benzenedicarboxamide as a whine crystalline solid (23.95 g, 79.5% yield), m.p. 231°-3°.

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