title: Iridium-catalyzed C-H borylation of pyridines.
abstract: The iridium-catalysed C-H borylation is a valuable and attractive method for the preparation of aryl and heteroaryl boronates. However, application of this methodology for the preparation of pyridyl and related azinyl boronates can be challenged by low reactivity and propensity for rapid protodeborylation, particularly for a boronate ester ortho to the azinyl nitrogen. Competition experiments have revealed that the low reactivity is due to inhibition of the active catalyst through coordination of the azinyl nitrogen lone pair at the vacant site on the iridium. This effect can be overcome through the incorporation of a substituent at C-2. Moreover, when this is sufficiently electron-withdrawing protodeborylation is sufficiently slowed to permit isolation and purification of the C-6 boronate ester. Following functionalization, reduction of the directing C-2 substituent provides the product arising from formal ortho borylation of an unhindered pyridine ring.
authors.affiliation: Department of Chemistry, Durham University, South Road, Durham, DH1 3LE, UK. p.g.steel@durham.ac.uk.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Sadler
authors.forename: Hazmi
authors.initials: H
authors.lastname: Tajuddin
authors.forename: Ibraheem A I
authors.initials: IA
authors.lastname: Mkhalid
authors.forename: Andrei S
authors.initials: AS
authors.lastname: Batsanov
authors.forename: David
authors.initials: D
authors.lastname: Albesa-Jove
authors.forename: Man Sing
authors.initials: MS
authors.lastname: Cheung
authors.forename: Aoife C
authors.initials: AC
authors.lastname: Maxwell
authors.forename: Lena
authors.initials: L
authors.lastname: Shukla
authors.forename: Bryan
authors.initials: B
authors.lastname: Roberts
authors.forename: David C
authors.initials: DC
authors.lastname: Blakemore
authors.forename: Zhenyang
authors.initials: Z
authors.lastname: Lin
authors.forename: Todd B
authors.initials: TB
authors.lastname: Marder
authors.forename: Patrick G
authors.initials: PG
authors.lastname: Steel
mesh_terms: D001896:Boron Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D007495:Iridium / Q000737:chemistry*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*
chemical_list: D001896:Boron Compounds; D009942:Organometallic Compounds; D011725:Pyridines; D007495:Iridium