title: Direct ortho-Arylation of Pyridinecarboxylic Acids: Overcoming the Deactivating Effect of sp2-Nitrogen.
abstract: Direct arylations of pyridines are challenging transformations due to the high Lewis basicity of the sp2-nitrogen. The use of carboxylates as directing groups is reported, facilitating the Pd-catalyzed C-H arylation of this difficult class of substrates. This methodology allows regioselective C3/C4 arylation, without the need to use solvent quantities of the pyridine, and using low-cost chloro- and bromoarenes as coupling partners. Furthermore, carboxylates could be employed as traceless directing groups through a one-pot C-H arylation/Cu(I)-mediated decarboxylation sequence, thereby accessing directing-group-free pyridine biaryls.
authors.affiliation: School of Biological and Chemical Sciences, Queen Mary University of London , Mile End Road, London E1 4NS, U.K.
authors.forename: Adam J S
authors.initials: AJ
authors.lastname: Johnston
authors.affiliation: Syngenta, Jealott's Hill International Research Centre , Bracknell, Berkshire RG42 6EY, U.K.
authors.forename: Kenneth B
authors.initials: KB
authors.lastname: Ling
authors.affiliation: Syngenta, Jealott's Hill International Research Centre , Bracknell, Berkshire RG42 6EY, U.K.
authors.forename: David
authors.initials: D
authors.lastname: Sale
authors.affiliation: School of Biological and Chemical Sciences, Queen Mary University of London , Mile End Road, London E1 4NS, U.K.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Lebrasseur
authors.affiliation: School of Chemistry, University of Manchester , Oxford Road, Manchester M13 9PL, U.K.
authors.forename: Igor
authors.initials: I
authors.lastname: Larrosa