Hydroacridines: part 29. 15N NMR chemical shifts of 9-substituted 1,2,3,4,5,6,7,8-octahydroacridines and their N-oxides-Taft, Swain-Lupton, and other types of linear correlations.

The (15)N NMR chemical shifts of 1,2,3,4,5,6,7,8-octahydroacridine, 12 of its 9-substituted derivatives, and of the corresponding N-oxides were measured and examined in terms of the 9-substituent effects and the effects of N-oxidation. For the 9-substituent effects, good linear correlations were found with the Taft and Swain-Lupton substituent constants, for both octahydroacridines and their N-oxides. The (15)N chemical shifts of both octahydroacridines and their N-oxides also correlate well, linearly with the (13)C chemical shifts of the para-carbons in analogously substituted benzene derivatives.Within the studied compounds, the magnitudes of the N-oxidation effects range from - 16.4 to - 27.4 ppm (shielding), and also correlate linearly with the Taft and Swain-Lupton substituent constants, as well as with the bond orders of the N(+)-O(-) bonds in the corresponding N-oxides. Furthermore, a very good linear correlation is found between the (15)N chemical shifts of octahydroacridines and those of the corresponding N-oxides. From the (15)N chemical shifts data, the Taft and Swain-Lupton substituent constants for the diacetylamino group (-NAc(2)) were evaluated in the present paper, as follows: sigma(R) = 0.07 and sigma(I) = 0.15; R = 0.08 and F= 0.20.
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