University of Hertfordshire

  • Pawel Kozielewicz
  • Petros Tsoungas
  • Mire Zloh
  • Demeter Tzeli
  • Ioannis Petsalakis
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Original languageEnglish
Pages (from-to)1711-1723
JournalStructural Chemistry
Journal publication dateDec 2014
Volume25
Issue6
Early online date1 May 2014
DOIs
Publication statusPublished - Dec 2014

Abstract

The structure and reactivity profile of prototype o-quinone methides 1, 2 and their ß-nitroso analogues 6-9 have been investigated by means of DFT and MP2 calculations. These highly reactive unstable species are generated by oxidative dearomatization of their precursor oximes. The destabilization of their structure is more pronounced in the ß-nitroso congeners 7-9. There is only a weak π conjugation across the nitrosoalkene arm. The latter gives rise to E and Z conformations and causes some distortion on the ring -frame while the π-frame is weakly perturbed. The Z conformation is the most stable in all structures. Their geometry is also affected by the o-quinone ring and the 1,2-(7 and 8) and 2,3-(9) isomer pattern. The stability of these conformations is rationalized in terms of ortho- or peri- ring formations. The impact of their geometry profile on their reactivity pattern has been studied by means of reactivity descriptors such as Fukui function f(r), chemical potential and hardness, HOMO and LUMO energies and their separation (HOMO-LUMO gap) as well as aromaticity indices such as HOMA and out-of-plane deformability. All descriptors consistently demonstrate that the reactivity is dominated by an intramolecular ortho or peri-cyclization mode to fused 1,2-oxazoles or 1,2-oxazines, respectively. Intermolecular primary reactions can occur at the quinone alkene bond or that of the nitrosoalkene arm.

ID: 2970211