NMR spectroscopic and theoretical structural study of 5-exo-methylene-substituted hydantoins

The H-1 and C-13 NMR spectra of a series of 3-phenyl-5-exo-methylene-substituted hydantoins were recorded and assigned unequivocally by the various methods of 1D and 2D NMR spectroscopy. Employing the NMR parameters thus obtained, the NOEs between the different protons within the molecules and the results of accompanying semiempirical (AM1 and PM3, respectively) and ab initio (3-21G*) quantum chemical calculations, the tautomerism, the acidity, the redox potentials, the stereochemistry and the electron density distribution of the hydantoins were studied, In addition, the X-ray crystallographic structure of compound 1r is given and compared with the spectroscopic results,