Electron-Deficient Aryl β-Diketones: Synthesis and Novel Tautomeric Preferences

✍ Scribed by Joseph C. Sloop; Paul D. Boyle; Augustus W. Fountain; William F. Pearman; Jacob A. Swann

• Publisher: John Wiley and Sons
• Year: 2010
• Tongue: English
• Weight: 326 KB
• Volume: 2011
• Category: Article
• ISSN: 1434-193X
• DOI: 10.1002/ejoc.201001451

✦ Synopsis

Abstract

Fluorinated aryl β‐diketones were prepared using Claisen and electrophilic fluorination methods. The keto–enol and enol–enol tautomerism of these compounds were examined in the solid state, as neat liquids and in polar, aprotic solution by crystallography and spectroscopy. Neat‐liquid spectroscopic measurements as well as single crystal X‐ray crystallographic results for selected electron‐deficient aryl β‐diketones suggest a single, chelated cis‐enol isomer that is conjugated with the aryl ring. In polar aprotic solvents, nonfluorinated aryl β‐diketones equilibrate rapidly from the chelated cis‐enol form to a tautomeric mixture of cis‐chelated enol and a substantial proportion of the diketone form, trifluoromethylated aryl β‐diketones show only limited equilibration from the chelated cis‐enol to the diketone form, with 2‐fluoro‐1‐aryl β‐diketones again displaying only the diketonic form.