Synthesis of carbazole-based selenaporphyrin via annulation.

Cu(I)-mediated alkoxylation of doubly 1,3-butadiyne-bridged carbazole dimer 1, followed by acid-catalyzed cyclization, provided furan-bridged carbazole dimer 3, while annulation reaction of 1 with selenium in the presence of hydrazine monohydrate provided selenophene-bridged carbazole dimer 5a. Oxidation of isophlorin 5a afforded carbazole-based selenaporphyrin 5b, which possessed distinct aromaticity and produced intensified and red-shifted absorption bands in the near-IR region.