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Updated: Jun 21, 2026

Preparation of Stable Bicyclic Aziridinium Ions and Their Ring-Opening for the Synthesis of Azaheterocycles
Published on: August 22, 2018
Synthesis of bicyclo[5.3.0]azulene derivatives
Donald D Nolting1, Michael Nickels, Ronald Price
1Department of Radiology and Radiological Sciences, Vanderbilt University Institute of Imaging Science, Nashville, TN, USA.
Abstract:
Azulene has been recognized for its application in medicinal therapy against inflammation. Recently, azulene analogs have been used in optical technology. Nevertheless, synthesis of this family of compounds is always associated with multiple challenges. In this protocol, we describe a time-efficient and cost-effective procedure for the preparation of azulene derivatives from 2-hydroxycyclohepta-2,4,6-trienone (tropolone), a readily available starting material. The technique illustrated here involves a cycloaddition reaction of a lactone with the in situ-generated vinyl ether from 2,2-dimethoxypropane during the thermolysis reaction. The three-step synthesis should take <4 d, resulting in an overall yield of 74% with a final step yield of 91%.
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