One‐Pot Rh(III)‐Catalyzed Twofold C−H Activation/Oxidative Annulation of N‐Arylpyrroles with Alkynes to Fluorescent Ullazines

Abstract

AbstractA range of densely functionalized ullazines have been synthesized by a one‐pot Rh(III)‐catalyzed twofold C−H activation/oxidative annulation of N‐arylpyrroles with alkynes. Electrophilic bromination at 5‐ or 5,7‐ positions of the EWG‐substituted ullazine core offers an interesting single or double entry for further extended functionalization. Mechanistic considerations suggest two complementary paths, EWG‐assisted and SEAr, for the C−H activations. All ullazines exhibit strong fluorescence emissions. Ullazines bearing thiophene and triarylamine units at 5‐ and 5,7‐ positions show a significant bathochromic shift in their emission spectra, attributed to the more extended electronic circuits present.