Scheme 1. Synthesis of Nitroimidazopyrazinones 17a–k.

(i) Various amines, TEA, DCM, 0 °C → rt; (ii) H₂SO₄/HNO₃, 60 °C; (iii) oxalyl chloride, catalytic DMF, DCM, 0 °C → rt, then concentrated NH₄OH, 0 °C → rt; (iv) bromoacetaldehyde diethyl acetal, K₂CO₃, μW 180 °C; (v) 2 M HCl/1,4-dioxane, μW 120 °C; (vi) various alkyl bromides, Cs₂CO₃ or K₂CO₃, DMF, μW 80–100 °C; (vii) K₂CO₃, MeOH, rt; (viii) various benzyl bromides, NaH, DMF, 0 °C → rt. ^aReported in a previous study.²⁶