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Cycloalkene budding: mass spectrometric studies of competitive and dual cycloalkene extrusion reactions from doubly unsaturated aldehyde N,N ‐dimethylhydrazones
Author(s) -
Weibel Douglas B.,
Attygalle Athula B.,
Shevy Laura E.,
Meinwald Jerrold
Publication year - 2000
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/1097-0231(20000715)14:13<1105::aid-rcm993>3.0.co;2-b
Subject(s) - chemistry , cycloalkene , cyclopentene , cyclohexene , fragmentation (computing) , stereochemistry , photochemistry , organic chemistry , hydrocarbon , catalysis , computer science , operating system
Mass spectral fragmentation pathways of four doubly unsaturated aldehyde N,N ‐dimethylhydrazones were investigated using EI‐MS and tandem mass spectrometry (MS/MS) under electron ionization and collisionally activated decomposition (CAD) conditions. Cyclopentene extrusion was found to be slightly favored over cyclohexene loss in a hydrazone capable of losing either cycloalkene. Evidence for the regeneration of a chain‐shortened iminium radical cation as a result of cycloalkene extrusion was provided by studying substrates capable of undergoing successive cycloalkene budding sequences. EI‐MS of these compounds shows sequential loss of both cyclopentene and cyclohexene, in accord with expectations for a cascade mechanism. Although these MS/MS experimental results are also compatible with alternative mechanisms which would entail the simultaneous loss of both neutral cycloalkenes or of a macrocyclic diene, a rapid cascade of cycloalkene budding accounts best for the experimental observations. Copyright © 2000 John Wiley & Sons, Ltd.