Gas-Phase Wittig Rearrangement of Carbanions Derived from Benzyl Ethers

Article abstract of DOI:10.1021/jo00376a006

The CA mass spectra of ions PhC^-HOR and Ph(R)CH-O^- (R = alkyl and phenyl) are very similar, suggesting that the Wittig rearrangement PhC^-HOEt -> Ph(Et)CH-O^- occurs in the gas phase.Major fragmentation can be interpreted in terms of 1,2-elimination of groups from the Wittig product ion.For example, 2H labeling of PhC^-HOEt and Ph(Et)CH-O^- show that the major processes produce Me-CH=CH-O^- + C6H6 and (C6H4)^-CHO + C2H6, with the latter process involving prior scrambling of phenyl hydrogens.An analogous process, Ph2CH-O^- -> (C6H4)^-CHO + C6H6 gives the major peak in the spectrum of "PhC^-HOPh".