A 13 C NMR spectroscopy study of the structure of N-H pyrazoles and indazoles

Abstract

The 13 C chemical shifts and some 1 H– 13 C coupling constants of 23 pyrazoles and indazoles are reported and discussed. The spectra were recorded in CDCl 3 and in DMSO-d 6 solutions and, in several cases, also in the solid state (CP/MAS technique). These data allow us to determine the tautomerism of these compounds in the solid state (usually only one tautomer) and in solution. The position of the tautomeric equilibrium is related to the Hammett σ m value of the 3(5)-substituent.