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On the Synthesis, Characterization and Reactivity of N‐Heteroaryl–Boryl Radicals, a New Radical Class Based on Five‐Membered Ring Ligands
Author(s) -
Tehfe MohamadAli,
Schweizer Stéphane,
Chany AnneCaroline,
Ysacco Cédric,
Clément JeanLouis,
Gigmes Didier,
MorletSavary Fabrice,
Fouassier JeanPierre,
Neuburger Markus,
Tschamber Théophile,
Blanchard Nicolas,
Lalevée Jacques
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201400197
Subject(s) - chemistry , radical , reactivity (psychology) , bond dissociation energy , hydrogen atom abstraction , intramolecular force , pyrazole , medicinal chemistry , ring (chemistry) , photochemistry , halogen , molecule , alkyl , stereochemistry , organic chemistry , medicine , alternative medicine , pathology
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(sp 2 ) complexation site. These pyrazole–boranes and pyrazaboles exhibit a low bond dissociation energy (BDE; BH) and accordingly excellent hydrogen transfer properties. Most importantly, a high modulation of the BDE(BH) 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 O 2 , 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.