M. Ahmad, G. Dahlke, S. Kass
Feb 14, 1996
Citations
0
Influential Citations
16
Citations
Journal
Journal of the American Chemical Society
Abstract
The thio-Wittig rearrangement of deprotonated allyl methyl sulfide has been examined in the gas phase with a variable temperature flowing afterglow-triple quadrupole device. Collision-induced dissociation studies of a series of thiolate anions (RS-) reveal that methyl deprotonation leads to 3-butene-1-thiolate (2a), the [2,3]-Wittig product, while 1-thiomethylallyl anion (1a) isomerizes to 1-butenyl thiolate (4a), the [1,4]-Wittig product, at elevated temperatures. Activation energies for these processes have been estimated using the Arrhenius equation and are compared to high-level (G2) calculations for the homolytic and heterolytic bond dissociation energies. Stepwise and concerted [1,4] pathways are found to have similar energy requirements, which accounts for some of the mechanistic controversy regarding these transformations in solution. The observed selectivity, [1,2] vs [1,4], is most easily accommodated by a concerted process but can be explained in terms of a stepwise mechanism by considering the...