The mass spectra of cinnolines and their N‐oxides

The mass spectra of cinnoline and various alkyl derivatives, and their 1- and 2-mono-oxides and 1,2-dioxides and a quaternary salt have been investigated. The spectra are interpreted in the light of experiments with deutero and 15N labelled derivatives whose syntheses are described. The major fragmentation path for cinnoline is loss of nitrogen molecule while that for its homologues is loss of nitrogen plus a hydrogen atom in some instances. Various initial fragmentations occur with the N-oxides, and deoxygenation appears to be the dominant process; in both 4-methylcinnoline 1-oxide and 1,2-dioxide an important path is formation of a 3-methyl-anthranil cation by loss of HCN and HCNO respectively.