Mass spectral fragmentation patterns of heterocycles. IV . Tetracyclic phenothiazines. IX. Electron impact promoted mass spectral fragmentation of pyrrolo[3,2,1‐kl]phenothiazine

Abstract The mass spectral fragmentation patterns of pyrrolo[3, 2, 1‐kl]phenothiazine (1) and its 1, 10‐dideuterioderi‐vative [2] are reported. The site of deuterium substitution in 2 was established by examination of its 13C nuclear magnetic resonance spectrum. The heteroaromatic stability of 1 to electron impact is exemplified by the occurrence of the molecular ion as the base peak and the formation of a reasonably intense M2+ ion. An intense M‐1 ion is also observed. The more abundant fragment ions appear to result from sulfur ionization. Fragment ions arising from ionization of the nitrogen constitute only a small fraction of the total ion current. Proposed fragmentation pathways of 1 are supported by the detection of appropriate metastable ions, exact mass measurements, and electron impact spectrum of 2.