Cyclooctadecanonaene

  [18]annulene is an annulene with chemical formula C₁₈H₁₈. This hydrocarbon obeys the Hückel's rule and is therefore an aromatic compound. The compound was first synthesised by F. Sondheimer. The original synthesis started by trimerization of the di-alkyne 1,5-hexadiyne with copper(II) acetate in pyridine followed by deprotonation and isomerization with potassium tert-butoxide in tert-butanol and was concluded with hydrogen organic reduction with the Lindlar catalyst.

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Notes

1. In the literature and some internet references Sondheimer is misspelled as Sandheimer.