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A new family of phenanthroline ligands was prepared. Hydrolysis of 4,7-dihalogenated 1,10-phenanthroline-2,9-diamides in acidic media leads to the formation of the corresponding 4,7-oxygenated derivatives. These ligands can exist in different tautomeric forms. The tautomerism of 4,7-oxygenated phenanthroline diamides has been investigated using quantum chemical calculations. The unsymmetrical oxo-hydroxy tautomeric form was proved to be the most energetically advantageous according to the spectral data and X-ray analysis. It was shown that 4,7-difluoro derivatives undergo acid hydrolysis more easily when compared to 4,7-dichloro derivatives. The coordination chemistry of 4,7-oxygenated 1,10-phenanthroline-2,9-diamides toward some lanthanide nitrates was investigated. The structures of Ln-complexes thus formed were studied both in the solid state and in solution (XRD analysis and IR, NMR and UV spectroscopy). It was revealed that 4,7-oxygenated ligands adopt the dihydroxy tautomeric form upon coordination with lanthanide nitrates. [ABSTRACT FROM AUTHOR]

The reaction of 3-halo-5,6-dihydro-4 H -1,2-oxazine N -oxides with arynes was studied. Arynes were generated from o -silylaryl triflates and underwent consecutive [3 + 2]-cycloaddition/[4 + 2]-cycloreversion with N -oxides leading to substituted 3-vinyl-benzisoxazoles in high yields. In the presented sequence, 1,2-oxazine N -oxides act as surrogates of rarely employed unsaturated nitrile oxides. A broad substrate scope was demonstrated. The influence of the substitution pattern of an aryne on the reaction outcome was determined. In the presence of bulky substituents, polycyclic 4,4a-dihydro-3 H -benzofuro[3,2- c ][1,2]oxazines were selectively formed. Mechanistic schemes for the observed reaction pathways were proposed. The synthetic utility of the products was demonstrated by their follow-up modifications.

A new family of phenanthroline ligands was prepared. Hydrolysis of 4,7-dihalogenated 1,10-phenanthroline-2,9-diamides in acidic media leads to the formation of the corresponding 4,7-oxygenated derivatives. These ligands can exist in different tautomeric forms. The tautomerism of 4,7-oxygenated phenanthroline diamides has been investigated using quantum chemical calculations. The unsymmetrical oxo-hydroxy tautomeric form was proved to be the most energetically advantageous according to the spectral data and X-ray analysis. It was shown that 4,7-difluoro derivatives undergo acid hydrolysis more easily when compared to 4,7-dichloro derivatives. The coordination chemistry of 4,7-oxygenated 1,10-phenanthroline-2,9-diamides toward some lanthanide nitrates was investigated. The structures of Ln-complexes thus formed were studied both in the solid state and in solution (XRD analysis and IR, NMR and UV spectroscopy). It was revealed that 4,7-oxygenated ligands adopt the dihydroxy tautomeric form upon coordination with lanthanide nitrates.