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.