Substituent effects in the ring-chain tautomerism of 1,3-diaryl-2,3-dihydro-1H-naphth[1,2-e][1,3]oxazines

Condensation of Betti base analogue amino naphthols with substituted benzaldehydes led to 1,3-diaryl-2,3-dihydro-1H-naphth[1,2-e][1,3]oxazines () which proved to be three-component (r1–o–r2) tautomeric mixtures in CDCl3 at 300 K. The electronic effects of the 3-aryl groups on the ratios of the ring-chain tautomeric forms at equilibrium could be described by the equation log KX=ρσ++log KX=H. The value of the intercept was found to be strongly influenced by the steric arrangement of the 1,3-diaryl substituents.