Syntheses of mono-, di- and triethynylazulenes

Simple and productive routes to mono-, di- and triethynylazulenes are described. Azulenes ethynylated in the five-membered ring can be prepared on a multigram scale by Pd-catalyzed cross-coupling of iodo- or bromoazulenes with trimethylsilyl-acetylene and subsequent desilylation. 5,7-Diethynylazulene was synthesized by dibromomethylenation of the corresponding dialdehyde and subsequent dehydrobromination.