Alternating oligo(,-phenylenes) ruthenium catalyzed diol-diene benzannulation: orthogonality to cross-coupling enables nanographene and PAH construction.

Ruthenium(0) catalyzed diol-diene benzannulation is applied to the conversion of oligo(-phenylene vinylenes) , and to alternating oligo(,-phenylenes) , . Orthogonality with respect to conventional palladium catalyzed biaryl cross-coupling permits construction of -bromo-terminated alternating oligo(,-phenylenes) , , which can be engaged in Suzuki cross-coupling and Scholl oxidation. In this way, structurally homogeneous nanographenes are prepared. Nanographene , which incorporates 14 fused benzene rings, was characterized by single crystal X-ray diffraction. In a similar fashion, -bromo-terminated oligo(-phenylene ethane diol) , which contains a 1,3,5-trisubstituted benzene core, is converted to the soluble, structurally homogeneous hexa--hexabenzocoronene . A benzothiophene-terminated pentamer was prepared and subjected to Scholl oxidation to furnish the helical bis(benzothiophene)-fused picene derivative . The steady-state absorption and emission properties of nanographenes , ,,,, and were characterized. These studies illustrate how orthogonality of ruthenium(0) catalyzed diol-diene benzannulation with respect to classical biaryl cross-coupling streamlines oligophenylene and nanographene construction.