Synthesis of Methylene Bridged Bis-pyrrolo[3,2-c]carbazoles <i>via</i> an Unusual Vilsmeier–Haack Product of <i>N</i>-Ethylcarbazole

Abstract

<p>The unexpected result for the formylation of <i>N</i>-ethylcarbazole under the Vilsmeier–Haack conditions (POCl₃/DMF) led to the synthesis of novel methylene bridged bis-pyrrolo[3,2-c]carbazoles <i>via</i> Hemetsberger indole synthesis was reported. A plausible mechanism for the formation of unexpectedly synthesized 7,7′-methylene bis(9-ethyl-9H-carbazole-3-carbaldehyde) <b>4</b> was postulated. The full characterization data of dicarbazolylmethane <b>4</b> and the bis-pyrrolo carbazoles <b>10a-b</b> were obtained by utilizing ¹H NMR, ¹³C NMR, FT-IR, mass spectrometry and single crystal X-ray diffraction techniques.</p