Development of straightforward and efficient methods for rapid construction of nitrogen and sulfur-containing heterocyclic compounds is an important target in synthetic, medicinal chemistry and in drug design.1 For instance, heterocycles containing a 1,4-thiazine moiety as a class of pharmaceutically important compounds exhibit various pharmaceutical activities including antibacterial, antiprolifrative, anticancer, antiepileptic, anthelmintic, antihypertensive, antiviral, antifungal, antiinflammatory, antimalaria, and antithyroid. The first attempt to synthesize 1,4-thiazines was made by Charles Barkenbus in 1948.2 Subsequently, other methods for the synthesis of 1,4-thiazine derivatives and heterocycles containing a 1,4-thiazine moiety have been reported in the literature.1,3 Herein, we report an efficient one-pot synthetic approach to the synthesis of new 4-(1-(pyrimidin-4-yl)ethyl)-12H-pyrimido[4\\\',5\\\':5,6][1,4]thiazino[2,3-b]quinoxaline derivatives from 5-bromo-4-[1-(5-bromo- 2,6-dichloropyrimidin-4-yl)ethyl]-2-chloro-6-methylpyrimidine 2 obtained from compound 14 and 3-aminoquinoxaline-2-thiol 3 under mild conditions at room temperature.

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