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 |
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| Authors: | Sofia Telitel Anne‐Laure Vallet Darrin M. Flanigan Dr. Bernadette Graff Dr. Fabrice Morlet‐Savary Prof. Tomislav Rovis Prof. Jacques Lalevée Dr. Emmanuel Lacôte |
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| Affiliation: | 1. Institut de Science des Matériaux de Mulhouse IS2M ‐ UMR CNRS 7361, Université de Haute‐Alsace, 15 rue Jean Starcky, 68057 Mulhouse Cedex (France), Fax: (+33)?3‐89‐33‐60‐69;2. ICSN CNRS, Avenue de la Terrasse, 91198 Gif‐sur‐Yvette Cedex (France);3. Department of Chemistry, Colorado State University, Fort Collins, CO 80523 (USA);4. Université de Lyon, Institut de chimie de Lyon, UMR 5265 CNRS‐Université Lyon I‐ESCPE Lyon, 43 Bd du 11 novembre 1918, 69616 Villeurbanne Cedex (France), Fax: (+33)?4‐72‐43‐17‐95 |
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| Abstract: | 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. |
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| Keywords: | boranes carbenes radical reactions polymerization radicals |
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