A convenient synthesis of thiazolopyrimidines, thiazolodipyrimidines and heterocyclothiazolopyrimidines

Article abstract of DOI:10.1016/S0040-4020(01)80225-8

Ethyl 4-aryl-6-substituted-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxyla tes 1 reacted with bromomalononitrile (2) to give ethyl 3-amino-5-aryl-2-cyano-7-substituted-5H-thiazolo[3,2-a]pyrimidine-6-ca rboxylates 3. The latter compounds reacted with formic acid, hydroxylamine hydrochloride and with formamide to give 9H-3,4-dihydrothiazolo[3,2-a:4,5-b]dipyrimidine-8-carboxylates 5, 1H,8H-pyrazolo[3,4-d]thiazolo[3,2-a]pyrimidine-7-carboxylates 8 and 2,7-diaminothiazolo[4,5-d]pyrimidine (7), respectively. Compounds 1b,e reacted with chloroacetyl chloride to yield ethyl 5-aryl-3-oxo-7-substituted-2,3-dihydro-5H-thiazolo[3,2-a]pyrimidine-6- carboxylates 9a,b which coupled with arenediazonium chlorides to give the corresponding 2-arylhydrazone derivatives 10a,b. Compound 9a adds α-cyanocinnamonitriles 12a-c to yield ethyl 2-amino-4-aryl-3-cyano-9-(4-methoxyphenyl)-7-methyl-4H,9H-pyrano[2,3-d ]thiazolo[3,2-a]pyrimidine-8-carboxylates 13a-c. Refluxing 1b-d with phenacyl bromide produced ethyl 5-aryl-7-methyl-3-phenyl-5H-thiazolo[3,2-a]pyrimidine-6-carboxylates 14a-c.