title: Unexpected fragmentation of beta-substituted meso-tetraphenylporphyrins induced by high-energy collisional activation.
abstract: The protonated molecules and radical cations of meso-tetraphenylporphyrins with beta-pyrrolic substituents, when formed by fast atom bombardment (FAB) and subjected to high-energy collisions, give rise to unexpected fragment ions. The reaction involves hydrogen migration from the ortho position of the phenyl ring to the a atom of the substituent, with formation of an intramolecular, six-membered ring. The process is analogous to condensed-phase cyclizations described for the same type of compounds. The fragmentation requires the presence of a double bond in the substituent group attached to the pyrrolic ring. A rearrangement process involving anchimeric assistance by the phenyl group (analogous to an ortho effect) is proposed for the formation of these ions.
authors.affiliation: Department of Chemistry, University of Aveiro, Aveiro, Portugal. mrd@dq.ua.pt
authors.forename: M Rosario M
authors.initials: MR
authors.lastname: Domingues
authors.forename: M Graça O S
authors.initials: MG
authors.lastname: Marques
authors.forename: Cristina M A
authors.initials: CM
authors.lastname: Alonso
authors.forename: M Graça P M S
authors.initials: MG
authors.lastname: Neves
authors.forename: J A S
authors.initials: JA
authors.lastname: Cavaleiro
authors.forename: A J
authors.initials: AJ
authors.lastname: Ferrer-Correia
authors.forename: Olga V
authors.initials: OV
authors.lastname: Nemirovskiy
authors.forename: Michael L
authors.initials: ML
authors.lastname: Gross
mesh_terms: D000179:Acrylates / Q000737:chemistry; D002412:Cations; D003500:Cyclization; D006859:Hydrogen / Q000737:chemistry; D009574:Nitro Compounds / Q000737:chemistry; D011166:Porphyrins / Q000737:chemistry*; D011422:Propionates / Q000737:chemistry; D011522:Protons; D016339:Spectrometry, Mass, Fast Atom Bombardment; D014753:Vinyl Compounds / Q000737:chemistry
chemical_list: D000179:Acrylates; D002412:Cations; D009574:Nitro Compounds; D011166:Porphyrins; D011422:Propionates; D011522:Protons; D014753:Vinyl Compounds; D006859:Hydrogen