4- Chloro-2-substituted thieno pyrimidines

Ring chlorination of 2-amino(or substituted amino)thieno[3,4-d]pyrim-idin-4(3//)-ones 370 (90EUP404356) and 5,7-dihydro-2-(2-methylanilino) thieno[3,4-c/]pyrimidin-4(3//)-one 372 (91MIP1) in boiling phosphoryl chloride gave the respective 4-chloro compounds 371 (90EUP404356) and 373 (91MIP1). The displacement of chlorine from both these compounds by a variety of nucleophiles was also reported. 

The action of NaBH4 on 141 (X = X = Cl) gave 2-chloro-3,4-dihydro-thieno[3,4-d]pyrimidines 142, which were used for the synthesis of 2-substituted dihydrothieno[3,4-d]pyrimidines via nucleophilic substitution reactions (81JMC376). 

In the case of Y = C02Et, the reaction affords 5-hydroxy thienopyrimidines, which exist predominantly as the oxo form (118). Pyrimidines 119 starting compounds can be prepared by two methods. One of them involves substitution of the mercaptoacetic acid residue for the chlorine atom in 4-chloro-5-ethoxycarbonylpy-rimidines 120. Pyrimidines 119 are then cyclized in the presence of bases to thieno[2,3-<7]pyrimidin-5-ones 118 (1988JHC959, 1993INP13664). 

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