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.通过金属催化环异构化（metal-catalyzed cycloisomerization）反应，合成了取代基完全朝向螺旋内侧曲率的[5]螺烯（[5]Helicenes）。此外，通过环异构化研究还发现了新型薁并螺烯（azulene-fused helicenes）。这类[5]螺烯具备足够高的构型稳定性，可通过手性固定相高效液相色谱（High Performance Liquid Chromatography, HPLC）实现对映异构体拆分。