REARRANGEMENTS IN THE MOLECULAR-IONS OF SOME ORTHO-SUBSTITUTED SCHIFF-BASES

Under electron ionization conditions, the ortho-substituted Schiff bas es N-benzylidene-o-toluidine (1a), N-(o-methylbenzylidene)aniline (1b) , N-salicylideneaniline (1c) and N-(o-methoxybenzylidene)aniline (1d) give fragment ions which have been shown by collision-activated mass-a nalysed ion kinetic energy spectra to have the structure of the proton ated molecular ions of indole (2), benzofuran (3), and 1,2-benzisoxazo le (4). The molecular ion of N-(o-methylbenzylidene)-o-toluidine (1f) gives as fragment ions not only the protonated molecular ion (2) of in dole and the tropylium ion but also the molecular ion of anthracene. A ttempts to find supporting evidence for a mechanism for this rearrange ment by deuterium labelling of a methyl group in (1b), such as (1g), h ave been unsuccessful.