Azulenes are the collective term for compounds which have a specific structure of ring-fused unsaturated seven-membered and five-membered rings, and they are named after Azur which is blue in Arabic. Three practical manufacturing methods are as followed:
The first method which was developed by Ziegler and Hafner is a reaction of ring-opened pyridinium salts or pyrylium salts with cyclopentadienides. The second one which was developed by Nozoe and Seto et al. is a reaction between tropone derivatives which substitutes halogen, methoxy, or tosyloxy groups at the 2 position, and the active methylene compounds such as cyanoacetates and malonates, in the presence of base. The last method which was developed by Yasunami and Takase et al. is a reaction with oxazulanones and enamines.
Hinokitiol which is well known tropolone derivative has antibacterial effect. Also colchicine which is alkaloid and contains tropolone ring shows strong antitumor effect. Tropolone compounds have possibilities in pharmaceutical field, especially for anticancer drugs.

Tropolones

Azulenes

Others

Tropolones

C0380	H0142	P0542
T0606	T1574

Azulenes

A0634

G0228

Others

M1188

I0657