13C NMR Spectroscopy: A Tool for Study of Conformational Analysis of 2-Aryl-trans-decahydroquinolin-4-ols

Abstract

In this investigation, proton decoupled 13C NMR Spectroscopy was used as a tool for the study of conformations of differently substituted 2-aryl-trans-decahydroquinolin-4-ols. The fusion of the rings in 2-aryl-trans-decahydroquinolin-4-ols was conclusively proved to be trans-, from a comparison of the experimental and calculated values. The signal assignments were made on the basis of the model system and in this case trans-decahydroquinoline was taken as model system. Substituent parameters for methyl, hydroxyl, and phenyl groups were derived from analogous systems and incorporated in the model system to obtain the calculated values. An examination of the 13C chemical shift values indicated that the configuration of the hydroxyl group was equatorial in all the α-forms of 2-aryl-trans-decahydroquinolin-4-ols and that of β-form’s was axial. In 3-Methyl-2-aryl-trans-decahydroquinolin-4-ols the chemical shifts suggested equatorial configuration to methyl and phenyl groups. Further, for 1-Methyl-2-aryl-trans-decahydroquinolin-4-ol and 1,3-dimethyl-2-aryl-trans-decahydroquinolin-4-ols the 1-or N-methyl group was found to has a greater preference to the equatorial position.