Picture map of Europe with pins indicating European capital cities

Open Access research with a European policy impact...

The Strathprints institutional repository is a digital archive of University of Strathclyde's Open Access research outputs. Strathprints provides access to thousands of Open Access research papers by Strathclyde researchers, including by researchers from the European Policies Research Centre (EPRC).

EPRC is a leading institute in Europe for comparative research on public policy, with a particular focus on regional development policies. Spanning 30 European countries, EPRC research programmes have a strong emphasis on applied research and knowledge exchange, including the provision of policy advice to EU institutions and national and sub-national government authorities throughout Europe.

Explore research outputs by the European Policies Research Centre...

Benzodifurantrione: a stable phenylogous enol

Lawrence, Anthony J. and Hutchings, Michael G. and Kennedy, Alan R. and McDouall, Joseph J. W. (2010) Benzodifurantrione: a stable phenylogous enol. Journal of Organic Chemistry, 75 (3). pp. 690-701. ISSN 0022-3263

Full text not available in this repository. Request a copy from the Strathclyde author

Abstract

The first example of a stable phenylogous enol, resulting from an extended keto-enol tautomerization across a benzene ring, is described. The enol has been isolated, and its structure was proven by X-ray crystallography. The equilibrium between the keto- and enol-tautomers has been extensively studied and quantified in solution by NMR and UV-vis spectroscopy. The position of equilibrium showed a linear correlation to the Kamlet-Taft solvatochromic scale for solvent H-bond acceptor strength (beta(OH)), and the equilibrium was proven to be fully dynamic, obeying first-order equilibrium kinetics. To attempt to explain why enolization occurs, at what surprisingly appears to be the expense of aromatic resonance stabilization, various structural features have been considered and explored further with the aid of MO calculations. Nucleus independent chemical shift (NICS) index of aromaticity calculations for each of the rings comprising both tautomers showed that while the central benzene ring loses aromaticity on enolization, the alpha-keto-lactone ring showed all unexpected and significant antiarornaticity in the keto-tautomer, which is by no means intuitive. The loss of stabilization energy associated with the central benzene ring is, therefore, to a certain degree compensated by removal of the antiaromatic destabilization of the alpha-keto-lactone ring rendering the two structures much closer in energy than would otherwise be expected.