Ziegler-Hafner synthesis

from Wikipedia, the free encyclopedia
Structure of the azulene

The Ziegler-Hafner synthesis is a versatile synthesis of azulene developed by Karl Ziegler and Klaus Hafner .

history

Azulene has been synthesized by a variety of methods, including the dehydrogenation of hydroazulenes . Of the known processes, the Ziegler-Hafner synthesis, a further development of the Zincke reaction , turned out to be one of the most versatile. For example, substituted azulenes can be produced by using substituted cyclopentadienes.

reaction

Azulene is produced by the condensation reaction of a cyclopentadienyl anion with an intermediate from the nucleophilic addition of dimethylamine to an activated pyridine derivative with ring opening , the Koenig's salt named after Walter Koenig . Klaus Hafner developed the method further over the years.

Ziegler-Hafner mechanism.svg

Individual evidence

  1. ^ Karl Ziegler, Klaus Hafner: A rational synthesis of the azulene. In: Angewandte Chemie 67, 1955, pp. 301-301, doi : 10.1002 / anie.19550671103 .
  2. ↑ Klaus Hafner: To the knowledge of the azulene I. A new azulene synthesis. In: Liebigs Annalen der Chemie 606, 1957, pp. 79-89, doi : 10.1002 / jlac.19576060109 .
  3. ↑ K. Hafner: Newer results of the azulene chemistry. In: Angewandte Chemie. 70, 1958, pp. 419-430, doi : 10.1002 / anie.19580701402 .