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Volumn 73, Issue 7, 2008, Pages 2811-2818

Correlated rotations in benzylfluorene derivatives: Structure, conformation, and stereodynamics

Author keywords

[No Author keywords available]

Indexed keywords

CONFORMATIONS; DENSITY FUNCTIONAL THEORY; ENANTIOMERS; NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY;

EID: 41649107327     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo7026917     Document Type: Article
Times cited : (11)

References (53)
  • 17
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    • Frisch, M. J, Trucks, G. W, Schlegel, H. B, Scuseria, G. E, Robb, M. A, Cheeseman, J. R, Montgomery, J. A, Jr, Vreven, T, Kudin, K. N, Burant, J. C, Millam, J. M, Iyengar, S. S, Tomasi, J, Barone, V, Mennucci, B, Cossi, M, Scalmani, G, Rega, N, Petersson, G. A, Nakatsuji, H, Hada, M, Ehara, M, Toyota, K, Fukuda, R, Hasegawa, J, Ishida, M, Nakajima, T, Honda, Y, Kitao, O, Nakai, H, Klene, M, Li, X, Knox, J. E, Hratchian, H. P, Cross, J. B, Bakken, V, Adamo, C, Jaramillo, J, Gomperts, R, Stratmann, R. E, Yazyev, O, Austin, A. J, Cammi, R, Pomelli, C, Ochterski, J. W, Ayala, P. Y, Morokuma, K, Voth, G. A, Salvador, P, Dannenberg, J. J, Zakrzewski, V. G, Dapprich, S, Daniels, A. D, Strain, M. C, Farkas, O, Malick, D. K, Rabuck, A. D, Raghavachari, K, Foresman, J. B, Ortiz, J. V, Cui, Q, Baboul, A. G, Clifford, S, Cioslowski, J, Stefanov, B. B, Liu, G, Liashenko, A, Piskorz, P, Komaromi, I, Martin, R. L, Fox, D. J, Keit
    • Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, T.; Kudin, K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone, V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene, M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; Morokuma, K.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich, S.; Daniels, A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M. W.; Gonzalez, C.; Pople, J. A. Gaussian 03, revision D.01; Gaussian, Inc.: Wallingford, CT, 2004.
  • 18
    • 41649083442 scopus 로고    scopus 로고
    • The different behaviour is a consequence of the fact that compound 2 is more hindered than 1, having two methyl groups in the ortho positions of the aryl substituent.
    • The different behaviour is a consequence of the fact that compound 2 is more hindered than 1, having two methyl groups in the ortho positions of the aryl substituent.
  • 19
    • 12244297937 scopus 로고    scopus 로고
    • At -141°C the H9 signal of the fluorenyl moiety (4.20 ppm) is sufficiently sharp as to display a double doublet, with J values equal to 4.5 and to 11 Hz. The larger of these values, according to the Karplus relationship (see Karplus, M. J. Am. Chem. Soc. 1963, 85, 2870-2871, is due to the coupling with Hβ, which is in an anti relationship to H9 (i.e, H9-C-C-Hβ dihedral angle ≈ 180°, whilst the smaller coupling is that with H α (i.e, H9-C-C-Hα dihedral angle ≈ 60°, The signal of Hα thus comprises the J ≈ 4.5 Hz and also the geminal coupling with Hβ J ≈ -15 Hz, Owing to the quite broad line width of the methylene signals below -140°C, however, a doublet signal is observed, because only the effect of major coupling is detectable. The signal of Hβ comprises the J ≈ 11 Hz and a
    • α (J ≈ -15 Hz). The combination of these two large couplings yields, in practice, a triplet signal since the difference between these two values cannot be detected, owing to the quite broad line width of the methylene signals below -140°C.
  • 20
    • 33947087968 scopus 로고
    • These processes bear some analogy with those indicated as ring-flip pathways by Mislow et al. See
    • These processes bear some analogy with those indicated as ring-flip pathways by Mislow et al. See: Gust, D.; Mislow, K. J. Am. Chem. Soc. 1972, 95, 1535-1547.
    • (1972) J. Am. Chem. Soc , vol.95 , pp. 1535-1547
    • Gust, D.1    Mislow, K.2
  • 24
    • 0003960193 scopus 로고
    • Lambert, J. B, Takeuchi, Y, Eds; VCH: New York, Chapter 4
    • Glaser, R. In Acyclic Organonitrogen Stereodynamics; Lambert, J. B., Takeuchi, Y., Eds; VCH: New York, 1992; Chapter 4.
    • (1992) Acyclic Organonitrogen Stereodynamics
    • Glaser, R.1
  • 31
    • 41649100939 scopus 로고    scopus 로고
    • The doublet due to the coupling with the isopropyl CH hydrogen is not visible anymore at low temperature in the case of the methyl signal of the ortho isopropyl groups because the corresponding line width is broadened by a second motion (see Figure 6) which begins to affect the spectrum. This broadening does not occur for the methyl signal of the para isopropyl group because the latter is not affected by the mentioned second motion
    • The doublet due to the coupling with the isopropyl CH hydrogen is not visible anymore at low temperature in the case of the methyl signal of the ortho isopropyl groups because the corresponding line width is broadened by a second motion (see Figure 6) which begins to affect the spectrum. This broadening does not occur for the methyl signal of the para isopropyl group because the latter is not affected by the mentioned second motion.
  • 36
    • 41649107353 scopus 로고    scopus 로고
    • The computed difference between the methyl shifts of conformers C and D is 0.77 ppm, which agrees well with the experimental separation of 0.83 ppm.
    • The computed difference between the methyl shifts of conformers C and D is 0.77 ppm, which agrees well with the experimental separation of 0.83 ppm.
  • 37
    • 41649095074 scopus 로고    scopus 로고
    • 2 signals of C and that the upfield signal of the latter is separated by that of D by 0.79 ppm, in fair agreement with the 0.69 ppm separation experimentally observed (Figure 7).
    • 2 signals of C and that the upfield signal of the latter is separated by that of D by 0.79 ppm, in fair agreement with the 0.69 ppm separation experimentally observed (Figure 7).
  • 43
    • 17444369440 scopus 로고    scopus 로고
    • A Situation where it has been unambiguously demonstrated that the X-ray diffraction structure in the solids is that of the minor conformer present in solution has been reported in: Lunazzi, L, Mazzanti, A, Minzoni, M, Anderson, J. E. Org. Lett. 2005, 7, 1291-1294
    • A Situation where it has been unambiguously demonstrated that the X-ray diffraction structure in the solids is that of the minor conformer present in solution has been reported in: Lunazzi, L.; Mazzanti, A.; Minzoni, M.; Anderson, J. E. Org. Lett. 2005, 7, 1291-1294.
  • 44
    • 0141677917 scopus 로고    scopus 로고
    • A recent example where the type of conformer observed in the crystal depends on the crystallisation solvent was reported in: Coluccini, C, Grilli, S, Lunazzi, L, Mazzanti, A. J. Org. Chem. 2003, 68, 7266-7273
    • A recent example where the type of conformer observed in the crystal depends on the crystallisation solvent was reported in: Coluccini, C.; Grilli, S.; Lunazzi, L.; Mazzanti, A. J. Org. Chem. 2003, 68, 7266-7273.
  • 45
    • 41649104179 scopus 로고    scopus 로고
    • The isopropyl methyl signals of 5 should be anisochronous in the -162°C spectrum of the major conformer, but the corresponding shift difference is smaller than the line width (about 85 Hz at this temperature). This is confirmed by the computed shift separation, which is predicted to be only 0.04 ppm (i.e., 24 Hz at 600 MHz).
    • The isopropyl methyl signals of 5 should be anisochronous in the -162°C spectrum of the major conformer, but the corresponding shift difference is smaller than the line width (about 85 Hz at this temperature). This is confirmed by the computed shift separation, which is predicted to be only 0.04 ppm (i.e., 24 Hz at 600 MHz).


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