Iridium-Catalyzed Borylation of Secondary C–H Bonds in Cyclic Ethers
摘要:
The borylation of secondary C-H bonds, specifically secondary C-H bonds of cyclic ethers, with a catalyst generated from tetramethylphenanthroline and an iridium precursor is reported. This borylation occurs with unique selectivity for the C-H bonds located beta to the oxygen atoms over the weaker C-H bonds located alpha to oxygen atoms. Mechanistic studies imply that the C-H bond cleavage occurs directly at the beta position rather than at the alpha position followed by isomerization of a reaction intermediate.
Iridium-catalysed borylation of sterically hindered C(sp<sup>3</sup>)–H bonds: remarkable rate acceleration by a catalytic amount of potassium tert-butoxide
The C(sp(3))-H bonds located on the methyl groups of an isopropyl group participate in iridium-catalysed C-H borylation with bis(pinacolato)diboron via a significant rate acceleration caused by a catalytic amount of t-BuOK.
β-C–H bonds in saturated heterocycles. Science, this issue p. 736 A methylphenanthroline iridium catalyst rapidly adds boron to primary C–Hbonds and beta C–Hbonds in saturated heterocycles. The selective functionalization of strong, typically inert carbon-hydrogen (C–H) bonds in organic molecules is changing synthetic chemistry. However, the undirected functionalization of primary C–Hbonds without
The hydroboration of three families of functionalized olefins (1-bromo- and 1,3-dibromopropenes, allylamines, 2,3-dihydrofuran) by pinacolborane and catecholborane has been studied under various experimental conditions. For 1-bromo- and 1,3-dibromopropenes, pinacolborane (PBH) is a poor reagent that requires the use of highpressure in ethereal solvents and provides only by-products, resulting from
Effect of Ligand Structure on the Electron Density and Activity of Iridium Catalysts for the Borylation of Alkanes
作者:Matthew A. Larsen、Raphael J. Oeschger、John F. Hartwig
DOI:10.1021/acscatal.0c00152
日期:2020.3.6
one another form catalysts for the borylation of alkyl C–H bonds with widely varying activity. This phenomenon was investigated computationally, and it was discovered that the stabilizing interactions between the phenanthroline ligand and the boryl ligands attached to Ir in the transition state for C–H oxidative addition could account for the differences in the activity of the catalysts that possess similar
Origin of the Difference in Reactivity between Ir Catalysts for the Borylation of C–H Bonds
作者:Raphael J. Oeschger、Matthew A. Larsen、Alessandro Bismuto、John F. Hartwig
DOI:10.1021/jacs.9b08920
日期:2019.10.16
A mechanistic study on the origin of the difference in reactivitybetween Ir catalysts for C-H borylation reactions is reported. Catalytic reactions of B2pin2 with a series of substrates that require high temperatures and long reaction times were conduct-ed. Reactions catalyzed by the combination of [Ir(COD)(OMe)]2 and 3,4,7,8-tetramethylphenanthroline (tmphen) occur in yields that are substantially