Mass spectrometric studies on 4-aryl-1-cyclopropyl-1,2-dihydropyridinyl derivatives: an examination of a novel fragmentation pathway.
Examination of the electrospray ionization product ion spectra of 1,2-dihydropyridinyl and 4-aryl-1,2-dihydropyridinyl derivatives bearing a 1-cyclopropyl or 1-trans-2-phenylcyclopropyl group has led to the characterization of unexpected fragment ions. For example, the base peak at m/z 156 present in the product ion spectrum of trans-1-(2-phenylcyclopropyl)-4-phenyl-1,2-dihydropyridine proved not to be the expected 4-phenylpyridinium species but rather the isomeric 3-phenyl-5-azoniafulvenyl species. The results of studies with a series of structural and isotopically labeled analogs require a novel fragmentation pathway to account for the formation of this and related fragment ions. One possible pathway is based on an initial 1,5-sigmatropic shift of a cyclopropylmethylene hydrogen atom that is accompanied by opening of the cyclopropyl ring. The resulting eniminium intermediates then fragment to yield the 5-azoniafulvenyl species.
Bissel
Philippe
P
Department of Chemistry, Virginia Tech, Blacksburg, VA 24061-0212, USA.
Geherin
Skye
S
Igarashi
Kazuo
K
Gandour
Richard D
RD
Lazar
Iulia M
IM
Castagnoli
Neal
N
D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine / Q000737:chemistry / Q000493:pharmacokinetics; D002412:Cations / Q000737:chemistry; D004095:Dihydropyridines / Q000032:analysis / Q000737:chemistry*; D004798:Enzymes / Q000378:metabolism; D006859:Hydrogen / Q000737:chemistry; D007536:Isomerism; D007554:Isotopes; D009498:Neurotoxins / Q000032:analysis / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization
D002412:Cations; D004095:Dihydropyridines; D004798:Enzymes; D007554:Isotopes; D009498:Neurotoxins; D006859:Hydrogen; D015632:1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine