Bissel P, Geherin S, Igarashi K, Gandour RD, Lazar IM, Castagnoli N. Mass spectrometric studies on 4-aryl-1-cyclopropyl-1,2-dihydropyridinyl derivatives: an examination of a novel fragmentation pathway.
JOURNAL OF MASS SPECTROMETRY : JMS 2006;
41:1643-53. [PMID:
17136767 DOI:
10.1002/jms.1135]
[Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
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.
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