Manufacturing Process
(a) Condensation in dimethylacetamide: To a suspension of 51.5 g of
anhydrous 3-amino-2,4,6-triiodo-benzoic acid (0.1 mol) in 100 ml of
dimethylacetamide were slowly added dropwise, while stirring, 15.5 g of
3,6,9-trioxaundecanediacid dichloride (0.06 mol), during which the
temperature gradually rose to about 50°C and the whole passed into solution.
After being stirred overnight, the solution was added dropwise to 1 liter of a
0.28 N solution of sodium hydroxide, and then 200 ml of 2 N hydrochloric acid
were cautiously added. The precipitate was filtered off with suction, washed
with water and dried. The yield was practically quantitative.
(b) Condensation in dioxan: 15.5 g of 3,6,9-trioxaundecane diacid dichloride
were added dropwise at about 95°C to a solution of 51.5 g of anhydrous 3-
amino-2,4,6-triiodo-benzoic acid in 52 ml of anhydrous dioxan. After further
stirring and heating for 3 hours, the solution was cooled, stirred dropwise into
500 ml of a 0.4 N solution of sodium hydroxide, and further worked up as
described in paragraph (a). The yield was practically quantitative.
(c) Purification: To the crude product obtained as described under paragraph
(a) or (b) in 300 ml of methanol was slowly added a quantity (about 15 ml) of
a 12 N solution of sodium hydroxide such that a test portion diluted with
water had a pH-value of 8 to 9. After stirring the mixture overnight, the
sodium salt of 3,6,9-trioxaundecane-1,11-dioyl-bis-(3-carboxy-2,4,6-triodoanilide) which crystallized out was filtered off with suction, was hed with
methanol and dried. Yield: 92 g (90% of the theoretical yield).
A solution of the salt in 900 ml of water was treated with active carbon, and
concentrated hydrochloric acid was added until the pH-value was 1. The
precipitate was filtered off with suction, washed with water, and dried at 50°C.
The yield of pure 3,6,9-trioxaundecane-1,11-dioyl-bis-(3-carboxy-2,4,6-
triiodo-anilide) was 80 g (80% of the theoretical yield). The substance melted
at 175°C with sintering.
