Ternary condensation of Biginelli thiones, chloroacetic acid, and aldehydes as an effective approach towards thiazolo[3,2-a] pyrimidines and 5-arylidenethiazolidine-2,4-diones

(Chemical Equation Presented) At the process of ethyl 6-methyl-4-aryl-2- thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylates condensation with aryl aldehydes and chloroacetic acid the unexpected formation of 5- arylidenethiazolidine-2,4-diones was determined in high yields as the reaction time was increased to 20 h. The latter represent the products of destructive hydrolyzes of ethyl 2-benzylidene-7-methyl-3-oxo-5-aryl-2,3-dihydro-5H-[1,3] thiazolo[3,2-a]pyrimidine-6-carboxylates which have been proved by independent synthesis.