Unexpected fragmentation of beta-substituted meso-tetraphenylporphyrins induced by high-energy collisional activation.
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.
Domingues
M Rosario M
MR
Department of Chemistry, University of Aveiro, Aveiro, Portugal. mrd@dq.ua.pt
Marques
M Graça O S
MG
Alonso
Cristina M A
CM
Neves
M Graça P M S
MG
Cavaleiro
J A S
JA
Ferrer-Correia
A J
AJ
Nemirovskiy
Olga V
OV
Gross
Michael L
ML
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
D000179:Acrylates; D002412:Cations; D009574:Nitro Compounds; D011166:Porphyrins; D011422:Propionates; D011522:Protons; D014753:Vinyl Compounds; D006859:Hydrogen