Sparr, C., Salamanova, E., Schweizer, W.B., Senn, H.M. and Gilmour, R. (2011) Theoretical and X-ray crystallographic evidence of a fluorine-imine gauche effect: an addendum to Dunathan's stereoelectronic hypothesis. Chemistry: A European Journal, 17(32), pp. 8850-8857. (doi: 10.1002/chem.201100644)
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Publisher's URL: http://dx.doi.org/10.1002/chem.201100644
Abstract
The preference of β-fluoroimines to adopt a <i>gauche</i> conformation has been studied by single-crystal X-ray diffraction analysis and DFT methods. Empirical and theoretical evidence for a preferential <i>gauche</i> arrangement around the NCCF torsion angle (φ) is presented ((<i>E</i>)-2-fluoro-<i>N</i>-(4-nitrobenzylidene)ethanamine: φ(NCCF) =70.0°). In the context of this study, the analysis of a pyridoxal-derived β-fluoroaldimine was performed, a species that is implicated in the inhibition of pyridoxal phosphate (PLP)-dependent enzymes by β-fluoroamine derivatives. The <i>gauche</i> preference of the internal aldimine (=NCH<sub>2</sub>CH<sub>2</sub>F) that can be rationalized by stereoelectronic arguments does not hold for the corresponding external system (N==CHCH<sub>2</sub>F) (<i>E</i><sub>min</sub> when φNCCF=120°). Moreover, the C--F bond is lengthened by more than 0.02Å at φNCCF=±90°, when it is exactly antiperiplanar to the conjugated imine. This activation of the C--F σ bond by an adjacent π system constitutes an addendum to Dunathan's stereoelectronic hypothesis.
| Item Type: | Articles |
|---|---|
| Keywords: | Aldimines, conformation analysis, density functional theory, fluorine, gauche effect |
| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | Senn, Dr Hans |
| Authors: | Sparr, C., Salamanova, E., Schweizer, W.B., Senn, H.M., and Gilmour, R. |
| Subjects: | Q Science > QD Chemistry |
| College/School: | College of Science and Engineering > School of Chemistry |
| Journal Name: | Chemistry: A European Journal |
| Journal Abbr.: | Chem. Eur J. |
| ISSN: | 0947-6539 |
| ISSN (Online): | 1521-3765 |
| Published Online: | 05 July 2011 |
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