Synthesis of fluoranthenes and indenocorannulenes: elucidation of chiral stereoisomers on the basis of static molecular bowls |
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Authors: | Wu Yao-Ting Hayama Tomoharu Baldridge Kim K Linden Anthony Siegel Jay S |
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Institution: | Institute of Organic Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland. |
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Abstract: | Cycloaromatization of a peri diyne with an external alkyne provides a general route to indeno-fused polynuclear aromatics. Fluoranthenes 9 (or 13) are easily accessible in good to excellent yields (75-99%; 18 examples) from the reaction of symmetric (or asymmetric) diynes 4 and alkynes 5 (or norbornadiene) in the presence of Wilkinson's catalyst. This formal (2+2)+2] cycloaddition can also be applied to generate various indenocorannulenes 28 from 2,3-diethynylcorannulene derivatives 27 and alkynes 5. The indenocorannulenes 28 exist in a static bowl form at room temperature with bowl-to-bowl inversion barriers higher than 24 kcal/mol. This barrier renders the rate of inversion slow enough at room temperature to establish a class of chiral, bowl-shaped stereoiomers containing no tetrahedrally ligated atoms. The crystal structure of 28g provides insight into the bowl-shaped geometry of these compounds. This new synthetic method occurs under neutral conditions and tolerates various functional groups (e.g., alkyl, aryl, alcohols, and esters). |
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