Synthesis of [5]Helicenes with a Substituent Exclusively on the Interior Side of the Helix by Metal-catalyzed Cycloisomerization

[5]Helicenes with a substituent exclusively oriented toward the interior curvature of the helix are synthesized by metal-catalyzed cycloisomerization. In addition, novel azulene-fused helicenes have been found through cycloisomerization studies. These [5]helicenes shows a high enough configurationally stability to allow resolution by HPLC on a chiral stationary phase.