Mass spectra of new substituted 2-amino-4H-pyrans: a retro-Diels-Alder reaction pattern

New substituted 2-amino-3-cyano-4H-pyrans have been studied by electron ion ization (EI), chemical ionization (CI) and electrospray ionization (ESI) ma ss spectrometry, The retro-Diels-Alder reaction (RDA) is the main fragmenta tion pattern observed in the EI spectra forming an unsaturated ketone as th e diene fragment. In contrast, a different RDA reaction takes place yieldin g an unsaturated amide as diene fragment together with the unsaturated keto ne 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. Copyright (C) 2000 John Wiley & Sons, Ltd.