Structural Study of 5-cyano-6-methoxy-3-methyl-3,4-dihydro-2-pyridone

The structure of 5-cyano-6-methoxy-3-methyl-3,4-dihydro-2-pyridone (3d) has been studied both in he solid state (X-ray diffraction) and in solution (H-1 NMR). Semiempirical calculations (AM1 and PM3) were also performed. The monocrystal (spatial group P-1, Z = 2) exhibits disorder, the R and S enantiomers being present in the asymmetric unit with a site occupation factor of 0.5. Both enantiomers show two similar conformations with a quasi-equatorial C3 methyl group. The semiempirical calculations agree with the structure and reactivity observed for 3d. A study of the coupling constants in the H-1 NMR spectrum of 3d has revealed that the major conformation present in solution coincides with that observed in the solid state.