Magnesium-catalysed hydroboration of pyridines: Kinetic analysis and poly-pyridine dearomatisation. (8th January 2016)

• Record Type: Journal Article
• Authors: Weetman, Catherine; Hill, Michael S.; Mahon, Mary F.
• Is Part Of: Polyhedron. Volume 103 Part A(2016)
• Page Start: 115
• Page End: 120
• Publication Date: 2016-01-08
• Subjects: Magnesium -- Catalysis -- Hydroboration -- Pyridine ligands -- Dearomatisation; Chemistry, Inorganic -- Periodicals; Chimie inorganique -- Périodiques; Organometaalverbindingen; Anorganische chemie; 546.05
• DOI: 10.1016/j.poly.2015.08.018
• Languages: English
• ISSNs: 0277-5387

Abstract

Graphical abstract: Kinetic analysis of the Mg-catalysed hydroboration of iso -quinoline with pinacol borane (HBpin) and studies of poly-pyridine dearomatisation, which are resistant to the hydroboration catalysis, have provided evidence that the catalysis proceeds via rate determining Mg–N/H–B metathesis of dearomatised pyridide anions. Abstract: A kinetic analysis of the hydroboration of iso -quinoline with pinacol borane (HBpin) and catalysed by a β-diketiminato magnesium n -butyl pre-catalyst has provided evidence that the reaction proceeds via rate determining Mg–N/H–B metathesis of a dearomatised iso -quinolide anion. The reaction rate is suppressed by increasing [ iso -quinoline] leading to the suggestion that catalytic turnover is also dependent on a pre-equilibrium involving dissociation of donor substrate molecules from the coordination sphere of the catalytic Mg centre. Stoichiometric reactions with a variety of poly-pyridine heterocycles have provided a range of magnesium derivatives of the dearomatised poly-pyridides either by alkyl or hydride transfer. The resistance of these latter species toward hydroboration is rationalised as a consequence of their additional coordinative stability providing corroborative evidence for the dissociative mechanism inferred from the kinetic analysis.