Contributing to Biochemistry and Optoelectronics: Pyrrolo[1′,2′:2,3]imidazo[1,5-Ia/I]indoles and Cyclohepta[4,5]pyrrolo[1,2-Ic/I]pyrrolo[1,2-Ia/I]imidazoles via [3+2] Annulation of Acylethynylcycloalka[Ib/I]pyrroles with Δ[sup.1]-Pyrrolines

Available pyrrolylalkynones with tetrahydroindolyl, cycloalkanopyrrolyl, and dihydrobenzo[g]indolyl moieties, acylethynylcycloalka[b]pyrroles, are readily annulated with Δ[sup.1]-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.