Regioselective substituent effects upon the synthesis of dipyrrins from 2-formyl pyrroles

Michael H. R. Beh (1) , Carlotta Figliola (1) , Kate-Lyn A. R. Lund (1) , Aleksandra K. Kajetanowicz (1) , Ann E. Johnsen (1) , Elise M. Aronitz (1) , Alison Thompson (1)

1 Dalhousie University [Halifax]

The synthesis of symmetric α-free meso-H-dipyrrin hydrobromides from 5-H-2-formyl pyrroles was investigated. The self-condensation produces regioisomeric dipyrrins through adoption of two mechanistic pathways. The key difference between the two pathways lies in which position of the pyrrole directs nucleophilic attack. Through a systematic study involving various substituted and (or) isotopically labelled 5-H-2-formyl pyrroles, we herein provide evidence to suggest that not only do two mechanistic pathways exist, but the steric bulk of the substituent adjacent to the 5-unsubstituted position influences which pathway dominates.

Mots clés: steric effects; condensation; synthesis; dipyrrins; pyrroles

Domaines: Chimie; Chimie organique

Michael H. R. Beh, Carlotta Figliola, Kate-Lyn A. R. Lund, Aleksandra K. Kajetanowicz, Ann E. Johnsen, et al.. Regioselective substituent effects upon the synthesis of dipyrrins from 2-formyl pyrroles. Canadian Journal of Chemistry, 2018, ⟨10.1139/cjc-2017-0662⟩. ⟨hal-01950271⟩