A Highly Configurationally Stable [4]Heterohelicenium Cation


  • We are grateful for financial support of this work by the Swiss National Science Foundation, the Federal Office for Education and Science, and the Sandoz Family Foundation (J.L.).


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A [4](hetero)helicenium cation was resolved using the hexacoordinated phosphorus-containing binphat anion (see picture: N, blue; O, red; C, gray). Its absolute configuration was determined by vibrational circular dichroism spectroscopy. The barrier of interconversion of its enantiomers is higher than that of [6]helicene.