title: Light-Induced Direct Arylation in the Solid Crystalline State as a Strategy Towards π-Expanded Imidazoles.
abstract: π-Expanded imidazoles bearing the 2-iodophenyl substituent at position 2 undergo direct photoinduced intramolecular arylation in the solid, crystalline state leading to large non-planar heterocycles. An analogous reaction employing 2-bromophenyl and 2-chlorophenyl substituents is considerably slower. Such processes have never before been demonstrated to occur in crystals and have allowed the efficient synthesizes of structurally unique compounds containing either the phenanthro[9',10':4,5]imidazo[1,2-f]phenanthridine moiety or structurally related skeletons. The reaction occurs in the thin crystalline layers irradiated with UV photons in an almost quantitative manner over 48-72 h. Several previously unknown architectures have been prepared using this methodology. Furthermore, the optical properties of these π-expanded imidazoles can be altered with the addition of heteroatoms and/or electron-donating groups.
authors.affiliation: Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44-52, 01-224, Warsaw, Poland.
authors.forename: Kamil
authors.initials: K
authors.lastname: Skonieczny
authors.affiliation: Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44-52, 01-224, Warsaw, Poland. dtgryko@icho.edu.pl.
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Gryko
keywords: arylation; fluorescence; fused-ring systems; nitrogen heterocycles; photochemistry