A facile and efficient one-pot synthesis of bench-stable quinoxaline N-oxides has been realized using α-oxoketene N,S-acetals and tert-butylnitrite (TBN) in open air viacascade annulation. The double functionalization of N,S-acetals proceeds through an unanticipated (Csp2)–H nitrosation by NO radical (generated in situ by TBN) and subsequent intramolecular N-arylation leading to quinoxaline, which