Elimination of Carbon Monoxide by Electron Impact on Quinoline N-oxide, Carbostyril and 8-Hydroxyquinoline

Article abstract of DOI:10.1002/oms.1210260412

Under electron impact, the molecular ions of quinoline N-oxide, carbostyril and 8-hydroxyquinoline lose carbon monoxide giving a fragment ion C8H7N (m/z 117), which was shown by collision-activated dissociation in each case to have the structure of the molecular ion of indole.Its formation from 8-hydroxyquinoline requires an unusual rearrangement.Isoquinoline N-oxide loses HCN rather than CO and gives a fragment which has the structure of the molecular ion of benzofuran.When the first three compounds were subjected to flash vacuum pyrolysis, quinoline N-oxide at 500-700 deg C gave carbostyril and indole was detected by gas chromatography/mass spectrometry.At 900 deg C carbostyril and 8-hydroxyquinoline both gave indole in small amounts, detected by gas chromatography/mass spectrometry.