Azolides. Part 12. Carbon-13 nuclear magnetic resonance study of N-methyl and N-acetyl derivatives of azoles and benzazoles

Abstract

¹³ C N.m.r. chemical shifts and C–H coupling constants of methyl- and acetyl-benzazoles have been derived from data for the corresponding uncondensed azoles by addition of increments which depend on the position and nature of the azole nitrogen atoms present. Use of ¹³C n.m.r. parameters by estimation of conformer distribution in acetylazoles or -benzazoles proved reliable only when the individual conformers were observable. In the absence of steric effects the composition of equilibrium mixtures of isomeric N-substituted azoles is independent of the nature of the N-substituent.