Fluoro-substituted 2-formylphenylboronic acids: Structures, properties and tautomeric equilibria

[Display omitted] Four isomeric fluoro-2-formylphenylboronic acids were synthesized and characterized by multinuclear NMR in solution. Crystal structures of two compounds have been determined by XRD. pKa values have been determined by spectrophotometric method. •Synthesis of isomeric fluoro-2-formylphenylboronic acids.•Multinuclear NMR characterization in solution.•Single crystal XRD measurements for 2 compounds.•pKa determination.•Tautomeric equilibrium. Four isomeric fluoro-2-formylphenylboronic acids were synthesized and characterized by 1H, 13C, 19F and 17O NMR. Molecular and crystal structure of two compounds was determined by single crystal XRD method. pKa values of all the isomers have been determined by spectrophotometric method and compared with the results for the corresponding benzoxaboroles as well as fluoro- and formylphenylboronic acids. Tautomeric equilibrium with cyclic benzoxaborole form was investigated. The influence of position of fluorine substituents on the properties of investigated compounds is discussed.