Stereochemistry of nitrogen heterocycles. 69. 13C NMR spectra of stereoisomeric 10-methyl-5-oxygen-substituted trans-decahydroquinolines

The ¹³C NMR spectra of 5-keto- and 5a- and 5e-hydroxy-10-methyl- and 1,10-dimethyltrans-decahydroquinolines have been recorded and interpreted. The increments of the oxo and hydroxy groups in the 10-methyldecahydroquinoline and the isostructural 10-methyldecaline systems were compared. The difference between the increments of azacyclic and the carbocyclic systems appears- at the -positions relative to the electronegative substituents (C₍₇₎ and C₍₉₎) and at the antiperiplanar -positions relative to nitrogen (C₍₅₎ and C₍₇₎). The increments of the oxo and the equatorial hydroxy groups in the aza ring are more shielded than in the carbon ring (at C₍₇₎, 2 ppm; at C_(g), 1 ppm), while the increments of the axial hydroxy group are more deshielded (at C₍₅₎, 1.5–2.0 ppm; at C₍₉₎, 1.0–1.5 ppm). The more the respective carbon atoms of the heterocycle are hydrogenated, the stronger are the deshielding -effect and the shielding -effect of the methyl group on nitrogen.For Communication 68, see 1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 60–65, January, 1990.