1031 Research Article Received: 7 May 2009 Revised: 14 July 2009 Accepted: 26 July 2009 Published online in Wiley Interscience: 15 September 2009 (www.interscience.com) DOI 10.1002/mrc.2507 Hydroacridines: Part 30. 1 H and 13 C NMR spectra of 9-substituted 1,2,3,4,5,6,7,8- octahydroacridines and of their N-oxides Francisc Potmischil, a* Maria Marinescu, a Alina Nicolescu b and C ˇ alin Deleanu b,c The 1 H and 13 C 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 determined, assigned, and discussed in terms of 9-substituent effects and effects of N-oxidation. A good linear correlation was found between the 13 C chemical shifts of the aromatic carbons in octahydroacridines and those of respective carbons in the corresponding N-oxides. Copyright c  2009 John Wiley & Sons, Ltd. Keywords: NMR; 1 H NMR; 13 C NMR; chemical shifts; ortho-substituent effects; octahydroacridines; nitrogen heterocycles; aromatic amine oxides; steric effects Introduction 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 exam- ine and discuss the effects of 9-substituents and the ef- fects of N-oxidation upon the 1 H and 13 C NMR chemi- cal shifts of these compounds. In the last two decades, sym-octahydroacridine and its substituted derivatives gained much in interest as starting materials in the syntheses of hydrogen-bonding receptors for biomolecules, [2–7] of metal- bonding polyaza torands, [7–9] and of other polyaza cavity-shaped ligands. [7,9 – 13] Results and Discussion The compounds under consideration were 1,2,3,4,5,6,7,8- octahydroacridine (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-1,2,3,4,5,6,7,8- octahydroacridine (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 -10- oxide (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. [4] The experience we gained with 1a – 13a enabled us to correct and complete, respectively, the assignments for 14a, as shown in Tables 1 and 3. The chemical shift assignments were performed on the basis of relative signal intensities, of spin–spin decoupling experiments, and of 2D HMQC, HMBC, and 1 H, 1 H-COSY experiments, as appro- priate. Due to their predominant octahydroacridone structures (see Scheme 2), compounds 13a and 13b show some atyp- ical chemical shifts as compared with 1a – 12a and 1b – 12b, respectively, and therefore 13a and 13b generally were not con- sidered in the discussion on the effects of 9-substituents and of N-oxidation upon the 1 H and 13 C chemical shifts of these compounds. 1 H NMR spectra The octahydroacridine moieties in compounds 1a – 10a, 13a and 1b – 10b, 13b show four signals, generated by the protons H-1,8, H-2,7, H-3,6, and H-4,5 with the chemical shifts listed in Tables 1 and 2, respectively. The protons H-1,8 Protons H-1,8 give rise to unsharp, slightly asymmetric triplets. Within the limits of experimental error, they show identi- ∗ Correspondence to: Francisc Potmischil, Department of Organic Chemistry, University of Bucharest, Bulevardul Regina Elisabeta 4-12, RO-030018 Bucharest-1, Romania. E-mail: potmisch@yahoo.com a Department of Organic Chemistry, University of Bucharest, Bulevardul Regina Elisabeta 4-12, RO-030018 Bucharest-1, Romania b ‘‘Petru Poni’’ Institute of Macromolecular Chemistry, Group of Biospectroscopy, Aleea Grigore Ghica 41A, RO-6600 Ias ¸i, Romania c National NMR Laboratory, ‘‘C. D. Nenit ¸escu’’ Institute of Organic Chemistry, Spl. Independent ¸ei 202 B, RO-060023 Bucharest-15, Romania Magn. Reson. Chem. 2009, 47, 1031–1035 Copyright c  2009 John Wiley & Sons, Ltd.