Download PDF
Synthesis 1994; 1994(12): 1418-1428
DOI: 10.1055/s-1994-25706
paper
© Georg Thieme Verlag, Rüdigerstr. 14, 70469 Stuttgart, Germany. All rights reserved. This journal, including all individual contributions and illustrations published therein, is legally protected by copyright for the duration of the copyright period. Any use, exploitation or commercialization outside the narrow limits set by copyright legislation, without the publisher's consent, is illegal and liable to criminal prosecution. This applies in particular to photostat reproduction, copying, cyclostyling, mimeographing or duplication of any kind, translating, preparation of microfilms, and electronic data processing and storage.

Simple and Selective Oxidation of 6-Alkylazulene Derivatives

Masayuki Yokota* , Rei Koyama, Hiromi Hayashi, Satoko Uchibori, Tsuyoshi Tomiyama, Hiroshi Miyazaki
  • *Kotobuki Research Laboratories, Kotobuki Seiyaku Company, Ltd. 6351, Sakaki, Hanishina, Nagano J-389-06, Japan
Further Information

Publication History

Publication Date:
25 April 2002 (online)

  PDF Download  Permissions and Reprints All articles of this category

The simple and regioseletive oxidation of 6-alkylazulene derivatives with an electron-withdrawing substituent at the 1-position of the azulene ring is described. Oxidation with molecular oxygen proceeds smoothly in the presence of a base such as potassium acetate (KOAc) or tetrabutylammonium hydroxide (Bu4NOH), and appears to proceed via enolization of the azulene derivatives. Oxidation of 6-isopropylazulene derivatives gave tertiary alcohols, which were easily converted to primary alcohols. Oxidation of 6-methylazulene derivatives provided azulene-6-carboxylate derivatives but dimethhyl azulene-1,6-dicarboxylate, which had been obtained by the oxidation of methyl 6-methylazulene-1-carboxylate, was found to be reduced selectively at the 6-position by sodium borohydride (NaBH4). In contrast, demethoxycarbonylation of dimethyl azulene-1,6-di-carboxylate with anhydrous phosphoric acid (100%PA) proceeded selectively at the 1-position to give methyl azulene-6-carboxylate. Those compounds obtained by the oxidation of 6-alkylazulenes are useful key intermediates for further modifications of the side chains at the 6-position of azulenes.