Schiff Bases Derived from 6-Amino-2H-chromen-2-one. Synthesis and 1H NMR Spectra

A number of 6-arylmethylideneamino-2H-chromen-2-ones were synthesized by reaction of 6-amino-2H-chromen-2-one with aromatic and heterocyclic aldehydes. A linear relation was revealed between the chemical shifts of the azomethine CH=N proton and protons in the chromene ring, on the one hand, and Hammett constants σ of the para substituents, on the other. Formation of intramolecular hydrogen bond in ortho-hydroxy derivatives induces a downfield shift of signals from protons in positions 3–5, 7, and 8 and CH=N proton (9-H) and upfield shift of the o-H signal (14-H).__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 7, 2005, pp. 1085–1091.Original Russian Text Copyright © 2005 by Ganushchak, Kobrin, Bilaya, Mizyuk.