A study of the norcaradiene–cycloheptatriene equilibrium in a series of azulenones by NMR spectroscopy; the impact of substitution on the position of equilibrium

Lorraine M. Bateman; Orla A. McNamara; N. Rachael Buckley; Patrick O'Leary; Francis Harrington; Norma Kelly; Sarah O'Keeffe; Angela Stack; Shane O'Neill; Daniel G. McCarthy; Anita R. Maguire

doi:10.1039/C5OB01346A

A study of the norcaradiene–cycloheptatriene equilibrium in a series of azulenones by NMR spectroscopy; the impact of substitution on the position of equilibrium

Lorraine M. Bateman,^a Orla A. McNamara,^a N. Rachael Buckley,^a Patrick O'Leary,†^a Francis Harrington,^a Norma Kelly,^a Sarah O'Keeffe,^a Angela Stack,^a Shane O'Neill,^a Daniel G. McCarthy^a and Anita R. Maguire*^b

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^a Department of Chemistry, Analytical and Biological Chemistry Research Facility, University College Cork, Ireland

^b Department of Chemistry and School of Pharmacy, Analytical and Biological Chemistry Research Facility, Synthesis and Solid State Pharmaceutical Centre, University College Cork, Ireland
E-mail: a.maguire@ucc.ie

Abstract

A systematic investigation of the influence of substitution at positions C-2 and C-3 on the azulenone skeleton, based on NMR characterisation, is discussed with particular focus on the impact of the steric and electronic characteristics of substituents on the position of the norcaradiene–cycloheptatriene (NCD–CHT) equilibrium. Variable temperature (VT) NMR studies, undertaken to enable the resolution of signals for the equilibrating valence tautomers revealed, in addition, interesting shifts in the equilibrium.

Organic & Biomolecular Chemistry

A study of the norcaradiene–cycloheptatriene equilibrium in a series of azulenones by NMR spectroscopy; the impact of substitution on the position of equilibrium

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A study of the norcaradiene–cycloheptatriene equilibrium in a series of azulenones by NMR spectroscopy; the impact of substitution on the position of equilibrium

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