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On Azahelicenes: Synthesis, Resolution, Properties and Applications
Míšek, Jiří
Mgr. Jiří Míšek PhD Thesis Abstract A novel and modular approach to azahelicenes has been developed. Using [2+2+2] cyclotrimerisation of appropriate triyne as a key step, azahelicenes 83, 84 and 85 have been prepared (Scheme 1). Scheme 1. Aza[6]helicenes 84 and 85 have shown to be sufficiently configurationally stable and have been resolve into individual enantiomers by the diastereoisomeric salt crystalisation and chiral HPLC. This allowed to determine exact values of racemisation barriers for both aza[6]helicenes 84 and 85. In general, both hexacyclic derivatives 84 and 85 are stable enough to be used in asymmetric transformations or chiral sensing. The ability of aza[6]helicenes 84 and 85 to serve as chiral ligands for transition metals has been proven by the preparation and X-ray analysis of corresponding silver complexes. Interesting chiral self-recogniton properties of aza[6]helicenes 84 in gas phase have been described using mass spectrometry techniques. In order to complement information about azahelicenes basicities, gas phase proton affinities of derivatives 84 and 85 and solution phase dissociation constants of azahelicenes 83, 84 and 85 have been determined. Eventually, the first utilization of azahelicene in asymmetric catalysis has been demonstrated by the successful use of optically pure...

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