An efficient synthesis of cytostatic mono and bis-alkynylpyrimidine derivatives by the Sonogashira cross-coupling reactions of 2,4-diamino-6-iodopyrimidine and 2-amino-4,6-dichloropyrimidine

A series of 6-alkynyl-2,4-diaminopyrimidine derivatives bearing various substituents at alkynyl moiety was prepared by the Sonogashira cross-coupling reaction of 2,4-diamino-6-iodopyrimidine using Pd(PPh3)2Cl2 as catalyst. The same reaction was applied to 2-amino-4,6-dichloropyrimidine. This compound on reaction with 1 equiv. of alkyne gave 6-alkynyl-2-amino-4-chloropyrimidine derivatives as main products, while reaction with three equivalents of alkyne afforded predominantly 4,6-bis-alkynyl-2-aminopyrimidines. Some of the resulting alkynyl pyrimidines showed considerable cytostatic activity.