Personne : Misal Castro, Luis Carlos
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Misal Castro
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Luis Carlos
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Université Laval. Département de chimie
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ncf13688668
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Publication Accès libre Metal-free borylation of heteroarenes using ambiphilic aminoboranes : on the importance of sterics in frustrated lewis pair C-H bond activation(American Chemical Society, 2017-10-18) Légaré-Lavergne, Julien; Fontaine, Frédéric-Georges; Misal Castro, Luis Carlos; Rochette, Étienne; Jayaraman, ArumugamTwo novel frustrated Lewis pair (FLP) aminoboranes, (1-Pip-2-BH2-C6H4)2 (2; Pip = piperidyl) and (1-NEt2-2-BH2-C6H4)2 (3; NEt2 = diethylamino), were synthesized, and their structural features were elucidated both in solution and in the solid state. The reactivity of these species for the borylation of heteroarenes was investigated and compared to previously reported (1-TMP-2-BH2-C6H4)2 (1; TMP = tetramethylpiperidyl) and (1-NMe2-2-BH2-C6H4)2 (4; NMe2 = dimethylamino). It was shown that 2 and 3 are more active catalysts for the borylation of heteroarenes than the bulkier analogue 1. Kinetic studies and density functional theory calculations were performed with 1 and 2 to ascertain the influence of the amino group of this FLP-catalyzed transformation. The C–H activation step was found to be more facile with smaller amines at the expense of a more difficult dissociation of the dimeric species. The bench-stable fluoroborate salts of all catalysts (1F–4F) have been synthesized and tested for the borylation reaction. The new precatalysts 2F and 3F are showing higher reaction rates and yields for multigram-scale syntheses.Publication Accès libre Metal-free borylative dearomatization of indoles : exploring the divergent reactivity of aminoborane C–H borylation catalysts(Royal Society of Chemistry, 2018-05-07) Fontaine, Frédéric-Georges; Misal Castro, Luis Carlos; Jayaraman, Arumugam; Desrosiers, VincentWhile the dearomatization of indoles by carbon–boron bond forming reactions is new and quite promising, they are so far mainly metal-catalyzed. Here, we establish the use of metal-free catalysts in promoting such reactions in an atom-efficient way. The in situ generated ambiphilic aminoborane catalyst (1-Pip-2-BH2-C6H4)2 (Pip = piperidyl) promotes borylative dearomatization of various 1-arylsulfonyl indoles with pinacolborane in a syn addition fashion, with H and Bpin groups added respectively to the 2 and 3 positions of indoles. Catalysis proceeds with good to excellent conversion and essentially with complete regio- and diastereoselectivity. From mechanistic insights and DFT computations, we realized and established that prototypical boranes can also catalyze this borylative dearomatization.