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 (3-9) which proved to be three-component (r(1)-o-r(2)) 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 K-X=rhosigma(+)+log K-X=H. The value of the intercept was found to be strongly influenced by the steric arrangement of the 1,3-diaryl substituents. (C) 2003 Elsevier Science Ltd. All rights reserved.