P.M.R. study of intramolecular hydrogen bonding in ortho-amidoanilides and its relation to the spectra of α-acylamidocinnamamide

Abstract

Proton magnetic resonance spectra of some ortho-amido-benzanilides and -acetanilides have been studied. While the secondary amido substituents in the 2-position have been found to form a strong hydrogen bond with the anilide proton, the tertiary amide function is sterically prohibited from doing so with consequent shielding of H 6 from its normal position in the 2-methoxycarbonyl substituted anilides. The abnormal shielding of Hβ in α-acylamidocinnamamides observed earlier has been discussed in relation to the present findings. A convenient method for the preparation of ortho-amidoanilides has been described.