New two-step synthesis of N-(2-ethylhexyl)-2,7-diiodocarbazole as a monomer for conjugated polymers

A reasonably efficient two-step synthesis of N-(2-ethylhexyl)-2,7-diiodocarbazole is presented. In the first step, the 4,4′-diiodobiphenyl was nitrated to a mixture of 4,4′-diiodo-2-nitrobiphenyl and 4-iodo-4′-nitrobiphenyl. In the second step, the mixture of these compounds was converted by simultaneous carbazole ring closure and N-alkylation to the N-(2-ethylhexyl)-2,7-diiodocarbazole by means of tris(2-ethylhexyl) phosphite. The synthesis represents a shorter alternative to the known more tedious procedures. The prepared compound is a suitable monomer for synthesis of conjugated polymers for optoelectronic applications.