Baker, Wilson published the artcilePreparation of iodine-containing x-ray contrast substances. I. 3,5-Diiodo-4-pyridone-N-acetic acid (“Perabrodil”), Application of 2-(3,5-Diiodo-4-oxopyridin-1(4H)-yl)acetic acid, the publication is Journal of the Society of Chemical Industry, London (1943), 189-91, database is CAplus.
The synthesis of 3,5-diiodo-4-pyridone-1-acetic acid (I), m. 247°, used for the visulization of the urinary tract, was effected by the following steps: pyridine, containing 2% AlCl3, in (CHCl2)2 was treated with 1 mol. Br at room temperature for 48 hrs., thus forming 4-pyridylpyridinium bromide-HBr, the aqueous solution of which, after freeing from (CHCl2)2, was hydrolyzed at 150° for 8 hrs., giving rise to a solution of pyridine-HBr and 4(1)-pyridone (II). This mixture was iodinated directly in aqueous NaOH by boiling with iodine and by making the solution alternately acid with concentrated HCl and alk. with 20% NaOH, 6 times during the course of 1 hr. The mechanism of the iodination is obscure; the product is 3,5-diiodo-4-pyridone (III) obtained, on final acidification and treatment with SO2, as a cream-colored precipitate Moist III (250 g.) in warm aqueous NaOH (48 g. in 460 ml. H2O) was heated with 60 g. CH2ClCO2H for 1 hr. and then treated with powd. NaCl. The separated Na salt of I yielded 107 g. I on acidification. I is polymorphous, crystallizing from H2O in hexagonal plates, needles, or fernlike crystals.
Journal of the Society of Chemical Industry, London published new progress about 101-29-1. 101-29-1 belongs to iodides-buliding-blocks, auxiliary class Pyridine,Iodide,Carboxylic acid,Ketone, name is 2-(3,5-Diiodo-4-oxopyridin-1(4H)-yl)acetic acid, and the molecular formula is C7H5I2NO3, Application of 2-(3,5-Diiodo-4-oxopyridin-1(4H)-yl)acetic acid.
Referemce:
https://en.wikipedia.org/wiki/Iodide,
Iodide – an overview | ScienceDirect Topics – ScienceDirect.com