Electron Impact Induced Loss of C‐5/C‐8 Substituents of 1,2,3,4‐Tetrahydroisoquinolines, VI1): Synthesis and Mass Spectrometric Fragmentation of Dihydroindole Derivatives

The syntheses of the C‐4 substituted dihydroindoles 25, 31 (scheme 7), and 36 (scheme 8) are described. ‐ The CID MIKE spectrum in the 2. field free region (2. FFR) of m/z 146 from 25 is very similar to but not identical with that of m/z 146 from the C‐5 substituted tetrahydroisoquinolines 3, 6, 7, and 8 (scheme 2), so supporting our hypothesis of a rearrangement in M+ of tetrahydroisoquinolines1) prior to fragmentation, but not proving it. As the CID MIKE spectra of the tetrahydroisoquinolines 3, 6, 7, and 8 are not identical among each other we assume that a 1.3‐H‐shift takes places in their M+ in competition to the rearrangement mentioned above.