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Influence of Electronic Effects on the Reactivity of Triazolylidene‐Boryl Radicals: Consequences for the use of N‐Heterocyclic Carbene Boranes in Organic and Polymer Synthesis
Author(s) -
Telitel Sofia,
Vallet AnneLaure,
Flanigan Darrin M.,
Graff Bernadette,
MorletSavary Fabrice,
Rovis Tomislav,
Lalevée Jacques,
Lacôte Emmanuel
Publication year - 2015
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.201500499
Subject(s) - reactivity (psychology) , radical , chemistry , carbene , boranes , photochemistry , flash photolysis , photopolymer , methyl acrylate , medicinal chemistry , polymer chemistry , organic chemistry , polymer , polymerization , reaction rate constant , kinetics , medicine , alternative medicine , pathology , boron , catalysis , physics , quantum mechanics , copolymer
A small library of triazolylidene‐boranes that differ only in the nature of the aryl group on the external nitrogen atom was prepared. Their reactivity as hydrogen‐atom donors, as well as that of the corresponding N‐heterocyclic carbene (NHC)‐boryl radicals toward methyl acrylate and oxygen, was investigated by laser flash photolysis, molecular orbital calculations, and ESR spin‐trapping experiments, and benchmarked relative to the already known dimethyltriazolylidene‐borane. The new NHC‐boranes were also used as co‐initiators for the Type I photopolymerization of acrylates. This allowed a structure–reactivity relationship with regard to the substitution pattern of the NHC to be established and the role of electronic effects in the reactivity of NHC‐boryl radicals to be probed. Although their rate of addition to methyl acrylate depends on their electronegativity, the radicals are all nucleophilic and good initiators for photopolymerization reactions.