Electron ionization‐induced fragmentation of 3‐cyclopropanospiro and 3‐cyclobutanospiro derivatives of Benzo‐ and pyridosultams

Electron ionization-induced fragmentations of 3-cyclopropanospiro and 3-cyclobutanospiro derivatives of selected benzo- and pyridosultams were studied and compared with the thermal decomposition of these compounds. 3-Cyclopropanospirobenzosultams and the corresponding pyridosultams were found to be thermally stable up to 400 °C. At higher temperatures they eliminate an SO 2 molecule yielding several dimethylindole derivatives together with other isomeric compounds. Loss of SO 2 is also the main fragmentation process of the molecular ions of these compounds with the exception of the 4-NO 2 derivative, for which elimination of CH 2 O is observed. 3-Cyclobutanospirobenzosultams and -pyridosultams eliminate SO 2 on heating above 200°C, yielding the corresponding 2-aryl-1,3-butadienes. Under EI conditions expulsion of SO 2 from the molecular ions is also observed. However, elimination of C 2 H 4 is the dominant process except for the 5-OCH 3 derivative.