- Microwave-assisted synthesis of some BI- and tricyclic pyrimidine derivatives
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Pyrimidine derivatives 4a-4c was prepared by a Biginelli cyclocondensation of β-ketoesters, aryl aldehydes, and thiourea derivatives under microwave irradiation. A simple and fast synthesis of bicyclic pyrimidine derivatives 6a-6c was performed by microwave-assisted reaction of 4a-4c with bromomalononitrile (5). Reaction of bicyclic pyrimidines 6a-6c with HCO2H and HONH3Cl under microwave irradiation gave tricyclic pyrimidines 7a-7c and 8a-8c respectively.
- Foroughifar,Mobinikhaledi,Jirandehi, H. Fathinejad,Memar
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p. 1269 - 1276
(2007/10/03)
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- A convenient synthesis of thiazolopyrimidines, thiazolodipyrimidines and heterocyclothiazolopyrimidines
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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.
- Sherif,Youssef,Mobarak,Abdel-Fattah
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p. 9561 - 9572
(2007/10/02)
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