Pyrylium salts

Pyrylium perchlorate

Pyrylium , outdated Pyroxoniumsalze , are a group of annular (cyclic), oxygen- containing chemical compounds that lead to the stable oxonium salts and heterocycles count. They are formally derived from pyrans , into which a third double bond has been introduced.

synthesis

The conversion of Grignard compounds with γ-pyrones and subsequent hydrolysis gives pyranols. Their reaction with strong acids gives pyrylium salts of the acid used with elimination of water . From chromones , benzopyrylium salts are formed analogously , from xanthone dibenzopyrylium salts (xanthylium salts).

The reaction of propene derivatives with carboxylic acid chlorides or anhydrides also leads to pyrylium salts in the presence of Lewis acids such as AlCl ₃ . This method is known as the Balaban reaction .

Individual evidence

1. ↑ Otto-Albrecht Neumüller (Ed.): Römpps Chemie-Lexikon. Volume 5: Pl-S. 8th revised and expanded edition. Franckh'sche Verlagshandlung, Stuttgart 1987, ISBN 3-440-04515-3 , pp. 3428-3429.
2. ^ Brockhaus ABC Chemie , VEB FA Brockhaus Verlag Leipzig 1965, p. 1151.
3. ^ Theophil Eicher, Siegfried Hauptmann , Andreas Speicher: The Chemistry of Heterocycles , Wilex-VCH, 2012, ISBN 978-3-527-32868-0 , p. 302.