Solution and solid state (CPMAS) NMR studies of the tautomerism of six-membered heterocyclic compounds related to 2-pyridones

Several 13C and 15N chemical shifts of 2-pyridone (1), 4(3H)-pyrimidone (2), uracil (3) and cytosine (4) have been measured in solution and in the solid state. These data have been discussed in relation with the tautomerism of the four heterocycles. GIAO ab initio calculations of absolute shieldings have been carried out to identify the predominant tautomers in the case of compounds (1) and (2).