Hydroacridines: part 29.¹⁵N NMR chemical shifts of 9‐substituted 1,2,3,4,5,6,7,8‐octahydroacridines and theirN‐oxides—Taft, Swain–Lupton, and other types of linear correlations

Abstract

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.

Schiff bases containing a furoxan moiety as potential nitric oxide donors in plant tissues

“…Assigning the site of N -oxidation in various natural or biological active compounds is important both for structural and mechanistic purposes related to metabolisation of these compounds. We have also previously investigated the influence of N -oxidation on 15 N- and 13 C-NMR spectra for series of octahydroacridines [ 50 , 51 ]. The shifts induced by N -oxidation to C-alpha (C3 in furoxan derivatives) and C-beta (C4 in furoxan derivatives) is consistent with our previous studies [ 51 ], and with early data on simple furoxan derivatives [ 52 ].…”

Hydroacridines: Part 30. 1H and 13C NMR spectra of 9‐substituted 1,2,3,4,5,6,7,8‐octahydroacridines and of their N‐oxides

“…The compounds under consideration were 1,2,3,4,5,6,7,8octahydroacridine (1a) [14] and -10-oxide (1b), [14] 9-ethyl-1,2,3,4,5,6,7,8-octahydroacridine (2a) [15] and -10-oxide (2b), [1] 9-chloro-1,2,3,4,5,6,7,8-octahydroacridine (3a), [16] and -10-oxide (3b), [16] 9-bromo-1,2,3,4,5,6,7,8-octahydroacridine (4a) [16] and -10-oxide, [16] 1,2,3,4,5,6,7,8-octahydro-9-methoxyacridine (5a) [16] and -10-oxide (5b), [16] 9-amino-1,2,3,4,5,6,7,8-octahydroacridine (6a) [16] and -10-oxide (6b), [16] 9-acetylamino-1,2,3,4,5,6,7,8octahydroacridine (7a) [16] and -10-oxide (7b), [16] 9-diacetylamino-1,2,3,4,5,6,7,8-octahydroacridine (8a) [16] and -10-oxide (8b), [16] 1,2,3,4,5,6,7,8-octahydro-9-nitroacridine (9a) [17] and -10-oxide (9b), [18] 9-(2-furyl)-1,2,3,4,5,6,7,8-octahydroacridine (10a) [19] and -10-oxide (10b), [1] 1,2,3,4,5,6,7,8-octahydro-9-(3-pyridyl)-acridine (11a) [14] and -10-oxide (11b), [14] 1,2,3,4,5,6,7,8-octahydro-9-(4-pyridyl)-acridine (12a) [14] and -10-oxide (12b), [14] and 1,2,3,4,5,6,7,8-octahydro-9-hydroxyacridine (13a) [16] and -10oxide (13b) [16] (Scheme 1). For 1,2,3,4,5,6,7,8-octahydroacridine-9-carboxylic acid ethyl ester (14a), 1 H NMR chemical shifts with two erroneously reversed assignments and 13 C chemical shifts with no assignment have been reported in the literature.…”

“…In our preceding work, [1] we have found a good linear correlation between the 15 N chemical shifts of the nitrogen atoms of the pyridine moiety in sym-octahydroacridines and those in the corresponding N-oxides, and therefrom it became obvious that similar correlations have to exist also between the 13 C chemical shifts of the carbon atoms of the pyridine moiety in octahydroacridines and in the corresponding N-oxides. Indeed, least squares regression analyses afforded Eqns (1), (2), and (3), which describe the correlations existing between the 13 C chemical a If not specified otherwise, the chemical shifts were measured in CDCl 3 solution.…”

“…In Part 29 of this series, [1] we have reported and discussed the 15 N NMR chemical shifts of 9-substituted derivatives of 1,2,3,4,5,6,7,8-octahydroacridine (sym-octahydroacridine) and of their 10-oxides (N-oxides). In the present article, we examine and discuss the effects of 9-substituents and the effects of N-oxidation upon the 1 H and 13 C NMR chemical shifts of these compounds.…”

Pyridine Compounds with Antimicrobial and Antiviral Activities

“…Marinescu et al [ 23 , 24 , 25 , 26 , 27 , 28 ] synthesized a series of tetrasubstituted pyridine-N-oxides (octahydroacridines) 38–41 , starting from the reaction of 2,2′-methylenedicyclohexanone with formamide at 167–170 °C and the separation of 1,2,3,4,5,6,7,8-octahydroacridine 36 from the reaction mixture ( Scheme 7 ). Oxidation of compound 36 with hydrogen peroxide and acetic acid gave the key intermediate 37 , sym -octahydroacridine-10-oxide, which, through reactions of nitration, reduction, alkylation, and hydrolysis, gave the compounds 38 , 39 , 40, and 41 .…”