Mass spectrometric study of linear and angular pyrrolodibenzofurans, pyrrolodibenzothiophenes, and pyrrolocarbazoles

The analysis of the mass spectra of unsubstituted pyrrolodibenzofurans and α-carboxy- and α-carbethoxypyrrolodibenzofurans, α-carboxy- and α-carbethoxypyrrolodibenzothiophenes, and α-carbethoxypyrrolocarbazoles, in which the pyrrole ring is fused to faces a, b, or c, permits finding the differences in the relative intensities of the peaks of their fragmentary ions due to the presence of additional free reactions in these structures or different internal stabilization of the fragmentary ions. The mass spectral characteristics which make it possible to identify the type of fusion of the pyrrole ring by comparison of the mass spectra of pairs of isomers are reported