Synthesis of Fluoranthenes and Indenocorannulenes: Elucidation of Chiral Stereoisomers on the Basis of Static Molecular Bowls

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).