title: Mass spectra of new substituted 2-amino-4H-pyrans: a retro-Diels-Alder reaction pattern.
abstract: New substituted 2-amino-3-cyano-4H-pyrans have been studied by electron ionization (EI), chemical ionization (CI) and electrospray ionization (ESI) mass spectrometry. The retro-Diels-Alder reaction (RDA) is the main fragmentation pattern observed in the EI spectra forming an unsaturated ketone as the diene fragment. In contrast, a different RDA reaction takes place yielding an unsaturated amide as diene fragment together with the unsaturated ketone in the CI spectra. The MS/MS spectra obtained using an ESI source reveal that the favoured fragmentation by collision induced dissociation (CID) is the elimination of the substituent at the C4 position with formation of a stable pyrilium cation.
authors.affiliation: Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Complutense, E-28040 Madrid, Spain.
authors.forename: A
authors.initials: A
authors.lastname: de Lucas
authors.forename: J
authors.initials: J
authors.lastname: Fernández-Gadea
authors.forename: N
authors.initials: N
authors.lastname: Martin
authors.forename: R
authors.initials: R
authors.lastname: Martínez
authors.forename: C
authors.initials: C
authors.lastname: Seoane
mesh_terms: D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D010879:Piperazines / Q000737:chemistry*; D011714:Pyrans / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D010879:Piperazines; D011714:Pyrans