Spectroscopic characterization of the 1-substituted 3,3-diphenyl-4-(2'-hydroxyphenyl)azetidin-2-ones: application of (13)C NMR, (1)H-(13)C COSY NMR and mass spectroscopy

The article deals with spectroscopic characterization of azetidin-2-ones. The presence of substituents like hydroxyl, fluoro, methoxy and benzhydryl, etc., on the azetidin-2-one ring significantly affects the IR absorption and (13)C NMR frequencies of the carbonyl group present in these compounds. The presence of an ester carbonyl group or too many methine protons in the molecule has been observed to limit the scope of IR and (1)H NMR spectroscopy in unambiguous assignment of the structure. The application of (13)C NMR, 2D NMR ((1)H-(13)C COSY) and mass spectroscopy in characterization of complex azetidin-2-ones is discussed. An application of the latter two techniques is described in deciding unequivocally between an azetidin-2-one ring and chroman-2-one ring structure for the product obtained by treatment of the 1-substituted 3,3-diphenyl-4-2'-(O-diphenylacyl)hydroxyphenyl]-2-azetidinones with ethanolic sodium hydroxide at room temperature.