反应详情

20 g (29 mmol) 3,5-diacetylamino-2,4,6-triiodobenzoic acid-2,3-dihydroxypropyl ester, which can be obtained from the sodium salt of 3,5-diacetylamino-2,4,6-triiodobenzoic acid by reaction with 3-chloropropane-1,2-diol at 105° C. (analogous to Organikum, 12th Edition, Deutscher Verlag der Wissenschaften, Berlin 1973, p.227 et seq.), are dissolved in 80 ml absolute pyridine and cooled to -10° C. To this solution is added dropwise 20 g (130 mmol) of commercially available methacrylic acid anhydride (Fluka) and the mixture is then stirred overnight at room temperature. The resulting clear reaction mixture is mixed with 1 l dilute hydrochloric acid and the white precipitate which forms is filtered off, washed with water to neutral and then reprecipitated from methanol/water. After drying in a fine vacuum (approx. 1 mbar, at room temperature) to a constant weight, 16.1 g (67.1%) colourless powder of amorphous appearance with a DSC melting point of 207° C. is obtained. 1 g of the substance is compressed as described in Example 1 into a tablet and irradiated; there is no discoloration.