In summary, new bis-pyrimidine derivatives (4a-g) were prepared in a three-step procedure based on 5-bromo-2,4-dichloro-6-methylpyrimidine (1) as starting material. In spite of our expectation based on our previous studies, the heterocyclization of compounds (3) and (4a-g) was not performed. It is proved that the poor electrophilicity of C-5 of these compounds can be responsible for synthesis of new bis-pyrimidine derivatives (4a-g) despite pyrimido[4,5-b][1,4]benzothiazine derivatives.

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