Solvent Moisture-Controlled Self-Assembly of Fused Benzoimidazopyrrolopyrazines with Different Ring’s Interposition

Abstract

This article shows that two extremely important families of fused heterocyclic assemblies, namely 6-methylbenzo[4,5]imidazo[1,2-a]pyrrolo[2,1-c]pyrazine and 5a-methyl-5a,6-dihydro-5H,12H-benzo[4,5]imidazo[1,2-a]pyrrolo[1,2-d]pyrazine, can be synthesized from only two available building blocks (N-allenylpyrrole-2-carbaldehyde and o-phenylenediamine) by controlling only one reaction parameter (water content of the medium). It should be emphasized that the latter class of compounds (with an a/d arrangement) is previously unknown. If the allene group is introduced not into the starting compound, but during the reaction (in superbase media), a heterocyclic ensemble, 5-methylbenzo[4,5]imidazo[1,2-a]pyrrolo[2,1-c]pyrazines, with a different position of the methyl group is formed.

Synthesis of Tetrazines from N-Allenylpyrrole-2-carbaldehydes and pH-Controlled Reversible Fragmentation

“…Previously, we have employed an original building block, Nallenylpyrrole-2-carbaldehyde, 5 as a key synthon for the construction of annulated pyrrole heterocycles to synthesize pyrrolopyrazine-N-oxides, 6 benzimidazopyrrolopyrazines, and dihydrobenzimidazopyrrolopyrazines. 7 The fundamental advantage of N-allenylpyrrole-2-carbaldehydes in cyclization reactions is that they allow the size of the closed ring to be easily controlled by varying the second reagent and substituents in the pyrrole counterpart. Theoretically, this can lead to different regioselectivities across the allene group.…”