Electron ionization-induced fragmentation of 3-cyclopropanospiro and 3-cyclobutanospiro derivatives of benzo- and pyridosultams

Electron ionization-induced fragmentations of 3-cyclopropanospiro and 3-cyc lobutanospiro derivatives of selected benzo- and pyridosultams were studied and compared with the thermal decomposition of these compounds. 3-Cyclopro panospirobenzosultams and the corresponding pyridosultams were found to be thermally stable up to 400 degreesC. At higher temperatures they eliminate an SO2 molecule yielding several dimethylindole derivatives together with o ther isomeric compounds. Loss of SO2 is also the main fragmentation process of the molecular ions of these compounds with the exception of the 4-NO2 d erivative, for which elimination of CH2O is observed. 3-Cyclobutanospiroben zosultams and -pyridosultams eliminate SO2 on heating above 200 degreesC, y ielding the corresponding 2-aryl-1,3-butadienes. Under EI conditions expuls ion of SO;? from the molecular ions is also observed. However, elimination of C2H4 is the dominant process except for the 5-OCH3 derivative. Copyright (C) 2001 John Wiley & Sons, Ltd.