240130-75-0Relevant academic research and scientific papers
Synthesis and x-ray analysis of new [5]helicenes - HMO calculations on the photocyclization of the stilbene precursors
Stammel, Christian,Froehlich, Roland,Wolff, Christian,Wenck, Hans,De Meijere, Armin,Mattay, Jochen
, p. 1709 - 1718 (2007/10/03)
The syntheses of the new pentahelicenes 5, 11, 17, 21, and 28 with various substituents are described. In the case of 2,13-dicyano-[5]helicene (11) optical resolution was achieved by HPLC using a column packed with γ- cyclodextrin. However, the enantiomers racemized within a few hours. On the other hand, the enantiomers of 28 turned out to be stable after separation on triacetylcellulose using MPLC. The crystal structures of 11, 17, and 21 were solved and indicated the typical distortions which are expected for helicenes. The model of the sum of free valence numbers was applied in order to rationalize the reactivity pattern of the photochemical phenanthrene cyclization.
