On the Synthesis,Characterization and Reactivity of N‐Heteroaryl–Boryl Radicals,a New Radical Class Based on Five‐Membered Ring Ligands |
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| Authors: | Dr Mohamad‐Ali Tehfe Dr Stéphane Schweizer Dr Anne‐Caroline Chany Dr Cédric Ysacco Dr Jean‐Louis Clément Dr Didier Gigmes Dr Fabrice Morlet‐Savary Prof Jean‐Pierre Fouassier Dr Markus Neuburger Dr Théophile Tschamber Dr Nicolas Blanchard Prof Jacques Lalevée |
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| Affiliation: | 1. Institut de Science des Matériaux de Mulhouse IS2M, UMR CNRS 7361, UHA, 15, rue Jean Starcky, 68057 Mulhouse Cedex (France);2. Université de Haute‐Alsace, ENSCMu, Laboratoire de Chimie Organique et Bioorganique, EA 4566, 3 rue Alfred Werner, 68093 Mulhouse Cedex (France);3. Aix‐Marseille Université, CNRS, Institut de Chimie Radicalaire, UMR CNRS 7273, 13397 Marseille, Cedex 20 (France);4. Formerly, ENSCMu, 3 rue Alfred Werner, 68093 Mulhouse Cedex (France);5. Department of Chemistry, University of Basel, Spitalstrasse 51, 4056 Basel (Switzerland);6. Université de Strasbourg, ECPM, Laboratoire de Chimie Moléculaire UMR CNRS 7509, 25 rue Becquerel, 67087 Strasbourg (France) |
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| Abstract: | The synthesis and physical characterization of a new class of N‐heterocycle–boryl radicals is presented, based on five membered ring ligands with a N(sp2) complexation site. These pyrazole–boranes and pyrazaboles exhibit a low bond dissociation energy (BDE; B?H) and accordingly excellent hydrogen transfer properties. Most importantly, a high modulation of the BDE(B?H) by the fine tuning of the N‐heterocyclic ligand was obtained in this series and could be correlated with the spin density on the boron atom of the corresponding radical. The reactivity of the latter for small molecule chemistry has been studied through the determination of several reaction rate constants corresponding to addition to alkenes and alkynes, addition to O2, oxidation by iodonium salts and halogen abstraction from alkyl halides. Two selected applications of N‐heterocycle–boryl radicals are also proposed herein, for radical polymerization and for radical dehalogenation reactions. |
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| Keywords: | boryl radicals co‐initiator dehalogenation N‐heterocycle– boranes polymerization radical chemistry |
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