Aromatic amides. XI. 1,3-Phenylenediamines and their diacyl derivatives

Abstract

In 4,6-disubstituted N,N'-(1,3-phenylene)bispivalamides, the ring hydrogen between the two amide groups is deshielded by both and consequently shows its ¹H nuclear magnetic resonance at extremely low field. Preferential stabilization of a particular amide configuration by dipole-dipole interactions gives rise to differential shielding effects in N,N'-(4-chloro-1,3-phenylene)bispivalamide and to strong deshielding of the aromatic C5-H in N,N'-(2-methylthiopyrimidine-4,6-diyl)bispivalamide.