1073353-68-0Relevant articles and documents
Cobalt-Catalyzed Borylation of Fluorinated Arenes: Thermodynamic Control of C(sp2)-H Oxidative Addition Results in ortho-to-Fluorine Selectivity
Pabst, Tyler P.,Obligacion, Jennifer V.,Rochette, étienne,Pappas, Iraklis,Chirik, Paul J.
, p. 15378 - 15389 (2019)
The mechanism of C(sp2)-H borylation of fluorinated arenes with B2Pin2 (Pin = pinacolato) catalyzed by bis(phosphino)pyridine (iPrPNP) cobalt complexes was studied to understand the origins of the uniquely high ortho-to-fluorine regioselectivity observed in these reactions. Variable time normalization analysis (VTNA) of reaction time courses and deuterium kinetic isotope effect measurements established a kinetic regime wherein C(sp2)-H oxidative addition is fast and reversible. Monitoring the reaction by in situ NMR spectroscopy revealed the intermediacy of a cobalt(I)-aryl complex that was generated with the same high ortho-to-fluorine regioselectivity associated with the overall catalytic transformation. Deuterium labeling experiments and stoichiometric studies established C(sp2)-H oxidative addition of the fluorinated arene as the selectivity-determining step of the reaction. This step favors the formation of ortho-fluoroaryl cobalt intermediates due to the ortho fluorine effect, a phenomenon whereby ortho fluorine substituents stabilize transition metal-carbon bonds. Computational studies provided evidence that the cobalt-carbon bonds of the relevant intermediates in (iPrPNP)Co-catalyzed borylation are strengthened with increasing ortho fluorine substitution. The atypical kinetic regime involving fast and reversible C(sp2)-H oxidative addition in combination with the thermodynamic preference for forming cobalt-aryl bonds adjacent to fluorinated sites are the origin of the high regioselectivity in the catalytic borylation reaction.
Transition metal-free synthesis of pinacol arylboronate: Regioselective boronation of 1,3-disubstituted benzenes
Wang, Yan,Wang, Le,Chen, Ling-Yan,Bhadury, Pinaki S.,Sun, Zhihua
, p. 675 - 678 (2014/05/06)
The regioselective synthesis of pinacol arylboronate has been achieved from 1,3-disubstituted benzene through directed ortho-metallation (DoM)-borylation sequence. A wide range of substituents and borylating reagents were investigated. In situ lithiation and subsequent boronation predominantly occurred at the ortho-position to afford the desired products in moderate yields. CSIRO 2014.
