Tautomerism of representative aromatic α-hydroxy carbaldehyde anils as studied by spectroscopic methods and AM1 calculations. Synthesis of 10-hydroxyphenanthrene-9-carbaldehyde

Abstract

The synthesis of 10-hydroxyphenanthrene-9-carbaldehyde and its anil are described. The structure of the latter compound has been thoroughly studied by 1H and 13C NMR, UV-visible absorption, fluorescence and IR spectroscopies. All the experimental results support the existence of this anil mainly in the keto-enamine tautomeric form. A comparison is presented with previously studied anils derived from salicylaldehyde and 2-hydroxynaphthalene-1-carbaldehyde. Semiempirical calculations (AM1) concerning the relative stability of tautomers as well as the optimized molecular geometries are in good agreement with the experimental findings