Synthesis, Structure and Basicity of 1,16-Diazahelicene

Article abstract of DOI:10.1016/S0040-4039(00)74406-6

The extension of 'proton sponges' 1 and 2 by further anellation to 1,16-diaza<6>helicene (3) was of interest to define scope and limitation of 'proton sponge' properties. 3 was prepared by photocyclisation of 2,7-bis(3-pyridylvinyl)naphthalene 4 and by Pd-catalyzed aryl-aryl coupling of the corresponding tetrabromo derivative 7.As consequence of the helical structure, 3 does not show 'proton sponge' basicity.X-ray structure analyses of 3 and 3*2HBr are in accordance with these findings.