The mechanism of dipyridamole (V) formation from 4, 8-dipiperidinopyrimido[5, 4-d]-pyrimidine-2, 6-disulfonyl dichloride (IV) and diethanolamine was examined : Reaction of 14Cdisu1fonamide (VI) with cold diethanolamine at 110-120°gave V. This reaction was thought to be an intramolecular rearrangement. Four compounds (VII, VIII, IX, X) were isolated as intermediates in the formation of V. The reaction of these compounds with diethanolamine gave V in a good yield. The reaction of sulfonamide compounds (VI, VII, IX) with a string base, such as sodium hydroxide solution or diethanolamine, gave aminoether compounds (VIII, X) by intramolecular rearrangement, and the effect of acid catalysis for the rate of intramolecular rearrangement of aminoether compounds was proved.
