Contributing to Biochemistry and Optoelectronics: Pyrrolo[1',2':2,3]imidazo[1,5- a]indoles and Cyclohepta[4,5]pyrrolo[1,2- c]pyrrolo[1,2- a]imidazoles via [3+2] Annulation of Acylethynylcycloalka[ b]pyrroles with Δ1-Pyrrolines

Abstract

Available pyrrolylalkynones with tetrahydroindolyl, cycloalkanopyrrolyl, and dihydrobenzo[g]indolyl moieties, acylethynylcycloalka[b]pyrroles, are readily annulated with Δ¹-pyrrolines (MeCN/THF, 70 °C, 8 h) to afford a series of novel pyrrolo[1',2':2,3]imidazo[1,5-a]indoles and cyclohepta[4,5]pyrrolo[1,2-c]pyrrolo[1,2-a]imidazoles functionalized with an acylethenyl group in up to an 81% yield. This original synthetic approach contributes to the arsenal of chemical methods promoting drug discovery. Photophysical studies show that some of the synthesized compounds, e.g., benzo[g]pyrroloimidazoindoles, are prospective candidates for TADF emitters of OLED.

Keywords: [3+2] annulation; acylethynylcycloalka[b]pyrroles; cyclohepta[4,5]pyrrolo[1,2-c]pyrrolo[1,2-a]imidazoles; pyrrolo[1′,2′:2,3]imidazo[1,5-a]indoles; Δ1-pyrrolines.