Mass Spectra of New Heterocycles: XXVII. Investigation of Polysubstituted 4,4'-Dipyrromethanes by Electron Ionization

Behavior of a wide range of previously unknown polysubstituted 4,4'-dipyrromethanes, namely 1,1'-bis{1-[2-(vinyloxy)ethyl]-2-amino-5-sulfanyl-1H-pyrrole-4-yl}ethanes, synthesized in one preparative stage from propargylamines, 2-(vinyloxy)ethyl isothiocyanate, and alkylating agents, under the action of electron ionization (70 eV) was studied for the first time. The studied compounds form a stable molecular ion {with the exception of 5.5'-di[(allyl-, propargyl-, and cyanomethyl)sulfanyl]dipyrromethanes}, the primary fragmentation of which proceeds in three directions with the formation of four key cations. Two of them (ions [M − R¹]⁺ and [M − SR¹]⁺) are associated with the breaking of C−S bonds in the sulfanyl substituent and between the latter and the pyrrole cycle. The third direction is due to the cleavage of the C−C bond between the pyrrole cycle and the methylene bridge linking the pyrrole cycles. In this case, two cations are formed, the peak intensity of which in the mass spectra ranges from 3 to 100% (depending on the structure of the substituents). The peaks of cation radicals [(M − R¹) − SR¹]^+• have the highest intensity (up to 100%). The resulting fragmentation ions are stabilized as a result of cyclization with the participation of a vinyloxyethyl substituent.