Synthesis, structure and ‘proton sponge’ properties of 1,12-bis(dimethylamino)benzo[c]phenanthrene

In continuation of earlier ‘proton sponge’ studies1, 1,2bis(dimethylamino)benzo[c]phenanthrene (2) was prepared in a multistep synthesis. In spite of its helical structure similar to diaza[6]helicene 1,2 shows in contrast to 1 ‘proton sponge’ properties due to the rotational flexibility of the dimethylamino groups as basic centers. X-Ray structure analyses are reported for 2 and its monoprotonated hydroiodide 3.