title: Ru-Catalyzed C-H Arylation of Fluoroarenes with Aryl Halides.
abstract: Although the ruthenium-catalyzed C-H arylation of arenes bearing directing groups with haloarenes is well-known, this process has never been achieved in the absence of directing groups. We report the first example of such a process and show that unexpectedly the reaction only takes place in the presence of catalytic amounts of a benzoic acid. Furthermore, contrary to other transition metals, the arylation site selectivity is governed by both electronic and steric factors. Stoichiometric and NMR mechanistic studies support a catalytic cycle that involves a well-defined η(6)-arene-ligand-free Ru(II) catalyst. Indeed, upon initial pivalate-assisted C-H activation, the aryl-Ru(II) intermediate generated is able to react with an aryl bromide coupling partner only in the presence of a benzoate additive. In contrast, directing-group-containing substrates (such as 2-phenylpyridine) do not require a benzoate additive. Deuterium labeling and kinetic isotope effect experiments indicate that C-H activation is both reversible and kinetically significant. Computational studies support a concerted metalation-deprotonation (CMD)-type ruthenation mode and shed light on the unusual arylation regioselectivity.
authors.affiliation: School of Chemistry, University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom.|School of Biological and Chemical Sciences, Queen Mary University of London , Mile End Road, London E1 4NS, United Kingdom.
authors.forename: Marco
authors.initials: M
authors.lastname: Simonetti
authors.affiliation: School of Chemistry, University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom.
authors.forename: Gregory J P
authors.initials: GJ
authors.lastname: Perry
authors.affiliation: School of Chemistry, University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom.
authors.forename: Xacobe C
authors.initials: XC
authors.lastname: Cambeiro
authors.affiliation: School of Biological and Chemical Sciences, Queen Mary University of London , Mile End Road, London E1 4NS, United Kingdom.
authors.forename: Francisco
authors.initials: F
authors.lastname: Juliá-Hernández
authors.affiliation: School of Biological and Chemical Sciences, Queen Mary University of London , Mile End Road, London E1 4NS, United Kingdom.
authors.forename: Jude N
authors.initials: JN
authors.lastname: Arokianathar
authors.affiliation: School of Chemistry, University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom.
authors.forename: Igor
authors.initials: I
authors.lastname: Larrosa