Synthesis of New Pyrimido[5′,4′:5,6][1,4]thiazino[2,3‐b]quinoxaline Derivatives in One Step

As a continuation of our search for new heterocyclic compounds, the synthesis of pyrimido[5′,4′:5,6][1,4]thiazino[2,3‐b]quinoxaline ring system is described. A series of new derivatives of this heterocyclic system ( 3a–d ) have been synthesized through the one‐pot heterocyclization of the appropriate 5‐amino6‐methylpyrimidine‐4‐thiols and 2,3‐dichloroquinoxaline in the presence of K₂CO₃ in dimethylformamide under reflux. N‐alkylation of the synthesized compounds with alkyl halides in KOH/dimethylformamide also gave the desired new derivatives of N‐alkylated pyrimido[5′,4′:5,6][1,4]thiazino[2,3‐b]quinoxalines ( 4a–h ). All the synthesized products were characterized and confirmed by their spectroscopic and microanalytical data.