C-13 SHIFTS IN 1-HETERA-2,6-DIARYL-4-CYCLOHEXANONES AND A FEW CORRESPONDING 1-HETERA-4-CYCLOHEXANOLS

The 13C NMR spectra of variously substituted l-hetera-4-cyclohexanones and some of the corresponding hetera-cyclohexanols have been measured and utilized in conformational analysis. The results have been interpreted in terms of deshielding effects for α and β carbons as exerted by the heteroatom. The data indicate an α-substituent effect in the order O > NCH3 > NH > S. A γ effect was observed for C(4) (C=0) which parallels that found for simple l-hetera-4-cyclohexanones: S < NH < O. Reductions of the ketones gave the corresponding alcohols, and conformations are assigned to a few 1-heteracyclohexanols on the basis of K, C chemical shifts also. Significantly great er Visch coupling values were observed for carbon atoms attached directly to sulfur compared to 1J13CH values for the C(3), C(5) carbons. Heteroatoms N and 0 cause greater chemical shifts in the resonances of antiperiplanar carbons than the sulfur counterpart as compared with model systems. Interestingly, 1Jc-D values for the carbon a to the C=O group or α to the hydroxyl-bearing carbon in the corresponding alcohols did not vary significantly (~20 Hz) in several cases. © 1979, American Chemical Society. All rights reserved.