Retro Diels–Alder and other electron ionization-induced fragmentation reactions of 1,2,3,4-tetrahydrobenzopyran-2,3-dicarboxylic acid derivatives

The electron ionization-induced fragmentation paths of various substituted 9,9a-dihydro-3aH-[1]benzopyrano[2,3-c]pyrrole-1,3-diones by use of metastable ions mass spectrometry have been studied. It was found that two main fragmentation pathways are representative for compounds under study. The first starts at the succinimide ring and its pattern mainly depends on the substituents in the benzene ring. The second one corresponds to the retro Diels–Alder reaction (RDA) that takes place at tetrahydropyran-type ring with charge migration.