Synthesis of carbazole-containing porphyrinoids by a multiple annulation strategy: A core-modified and π-expanded porphyrin

Going around in circles: The copper(I)-mediated annulation of a doubly 1,3-butadiyne-bridged carbazole dimer with amines or Na₂S provides isophlorins containing carbazole or thiophene-carbazole moieties, respectively (see scheme). Oxidization of the thiophene-containing isophlorin with MnO ₂ gives the corresponding porphyrin, which displays distinct aromaticity and remarkably intensified and red-shifted absorption bands in the near IR region.