Audran Gérard, Bikanga Raphael, Brémond Paul, Edeleva Mariya, Joly Jean-Patrick, Marque Sylvain R A, Nkolo Paulin, Roubaud Valérie
Aix Marseille Univ, CNRS, ICR, UMR 7273, case 551, Avenue Escadrille Normandie-Niemen, 13397 Marseille Cedex 20, France.
Laboratoire de Substances Naturelles et de Synthèse Organométalliques Université des Sciences et Techniques de Masuku, B.P. 943 Franceville, Gabon.
Org Biomol Chem. 2017 Oct 11;15(39):8425-8439. doi: 10.1039/c7ob02223a.
Recent amazing results (Nkolo et al., Org. Biomol. Chem., 2017, 6167) on the effect of solvents and polarity on the C-ON bond homolysis rate constants k of alkoxyamine RRNOR led us to re-investigate the antagonistic effect of intramolecular hydrogen-bonding (IHB) on k. Here, IHB is investigated both in the nitroxyl fragment RRNO and in the alkyl fragment R, as well as between fragments, that is, the donating group on the alkyl fragment and the accepting group on the nitroxyl fragment, and conversely. It appears that IHB between fragments (inter IHB) strikingly decreases the homolysis rate constant k, whereas IHB within the fragment (intra IHB) moderately increases k. For one alkoxyamine, the simultaneous occurrence of IHB within the nitroxyl fragment and between fragments is reported. The protonation effect is weaker in the presence than in the absence of IHB. A moderate solvent effect is also observed.
近期关于溶剂和极性对烷氧基胺RRNOR的C-ON键均裂速率常数k的影响取得了惊人的成果（恩科洛等人，《有机与生物分子化学》，2017年，6167页），这促使我们重新研究分子内氢键（IHB）对k的拮抗作用。在此，我们对硝酰基片段RRNO和烷基片段R中的IHB进行了研究，同时也研究了片段之间的IHB，即烷基片段上的供体基团与硝酰基片段上的受体基团之间的IHB，反之亦然。结果表明，片段间的IHB（片段间IHB）显著降低了均裂速率常数k，而片段内的IHB（片段内IHB）则适度增加了k。对于一种烷氧基胺，我们报道了硝酰基片段内和片段间同时存在IHB的情况。在存在IHB的情况下，质子化效应比不存在时更弱。同时还观察到了适度的溶剂效应。
