Chemistry of thienopyridines. XXIII. Mass spectra of some <i>N</i>‐oxides, sulfoxides, and sulfones

Abstract

Abstract The mass spectral fragmentation patterns of a series of thienopyridine N ‐oxides, S ‐oxides, and S,S ‐dioxides were elaborated as a means of structural determination. Observation of a significant (M‐16) peak is diagnostic for the presence of either an N ‐oxide or an S ‐oxide function (indistinguishable from one another by this method) but does not occur for an S,S ‐dioxide function. For a substituted thieno[2,3‐ b ]pyridine 7‐oxide, structural rearrangement to a pyridone (followed by emission of carbon monoxide or formyl radical) or side‐chain fission may be competitive with de‐ N ‐oxygenation. For two tricyclic parent S ‐oxides, rearrangement and de‐ S ‐oxygenation are competing initial processes. For parent S,S ‐dioxides structural rearrangement precedes fragmentation, wherein the oxygen is ejected in such forms as sulfur monoxide, carbon monoxide, formyl or cyanate radicals, and ketene.