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Volumn 72, Issue 7, 2007, Pages 2501-2507

Conformational consequences of the dynamic processes in the stereolabile atropisomers of acyl-substituted m-terphenyl derivatives

Author keywords

[No Author keywords available]

Indexed keywords

AROMATIC COMPOUNDS; CONFORMATIONS; COVALENT BONDS; ENANTIOMERS; NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY; STEREOCHEMISTRY; SUBSTITUTION REACTIONS;

EID: 34047198339     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo062558g     Document Type: Article
Times cited : (11)

References (39)
  • 5
    • 34047193285 scopus 로고    scopus 로고
    • Gaussian 03, revision D.01: Frisch, M. J, Trucks, G. W, Schlegel, H. B, Scuseria, G. E, Robb, M. A, Cheeseman, J. R, Montgomery, Jr, J. A, 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, Mar
    • Gaussian 03, revision D.01: Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Montgomery, Jr., J. A.; 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 Inc., Wallingford, CT, 2004.
  • 7
    • 34047242627 scopus 로고    scopus 로고
    • Since the cis to trans interconversion can be accomplished by the rotation of either of the two external aryl rings, the rate for the rotation of a single aryl ring corresponds to half of the measured rate constants. The corresponding barrier thus becomes 0.2 kcal mol-1 higher, and it is this value that, in principle, should be compared to the theoretical barrier
    • -1 higher, and it is this value that, in principle, should be compared to the theoretical barrier.
  • 8
    • 34047197866 scopus 로고    scopus 로고
    • The analysis of the population distribution might also be performed by taking into account the entropy of mixing the conformational enantiomers (see: Eliel, L. E, Wilen, S. H. Stereochemistry of Organic Compounds; John Wiley and Sons: New York, 1994; pp 97 and 601. Collet, A. In Problems and Wonders of Chiral Molecules; Simonyi, M, Ed, Akadémiai Kiadó: Budapest, 1990; p 93, The computed energy (0.08 kcal mol -1) of the chiral trans conformer is thus lowered by RT In 2 (i.e, 0.175 kcal mol-1 at -146 °C, becoming, therefore, 0.08-0.175, 0.095 kcal mol-1. On the basis of this correction, the previously computed relative energies of the three conformers (i.e, 0, 0.16, and 0.08 kcal mol-1) become 0.095, 0.255, and 0 kcal mol-1 for cis (syn, cis anti, and trans, respectively. These values correspond to theoretical populations of 33, 18, and 49, respectively, a trend which parallels the experimen
    • -1 for cis (syn), cis (anti), and trans, respectively. These values correspond to theoretical populations of 33%, 18%, and 49%, respectively, a trend which parallels the experimental ratio of 32%, 10%, and 58%.
  • 9
    • 34047235794 scopus 로고    scopus 로고
    • Further support for this assignment was obtained by means of the computations of the 13C chemical shifts (see the Experimental Section) of the trans conformer of 3. These calculations indicate that the upfield shift of the quaternary carbon bonded to the isopropyl moiety corresponds to that in the ring having a syn relationship to C=O, the downfield shift being that in the anti relationship. The experimental signal of the same carbon of the major (48, cis conformer is very close to the upfield shift of the trans conformer, whereas the experimental signal of the minor (12, cis conformer is close to the downfield shift of the trans conformer (Supporting Information Figure S-3, On this basis, it is thus conceivable to assign the cis (syn) structure to the major conformer and the cis (anti) structure to the minor conformer, in agreement with the trend of the computed energies
    • 13C chemical shifts (see the Experimental Section) of the trans conformer of 3. These calculations indicate that the upfield shift of the quaternary carbon bonded to the isopropyl moiety corresponds to that in the ring having a syn relationship to C=O, the downfield shift being that in the anti relationship. The experimental signal of the same carbon of the major (48%) cis conformer is very close to the upfield shift of the trans conformer, whereas the experimental signal of the minor (12%) cis conformer is close to the downfield shift of the trans conformer (Supporting Information Figure S-3). On this basis, it is thus conceivable to assign the cis (syn) structure to the major conformer and the cis (anti) structure to the minor conformer, in agreement with the trend of the computed energies.
  • 10
    • 34047234963 scopus 로고    scopus 로고
    • The integrated intensity distribution of the isopropyl methyl lines matches the ratio 47:40:13 derived from the other signals. In particular, the four lines expected for the trans isomer correspond to the 40% intensity.
    • The integrated intensity distribution of the isopropyl methyl lines matches the ratio 47:40:13 derived from the other signals. In particular, the four lines expected for the trans isomer correspond to the 40% intensity.
  • 11
    • 34047225566 scopus 로고    scopus 로고
    • -1.
    • -1.
  • 12
    • 34047210673 scopus 로고    scopus 로고
    • This value can still be compared to those obtained at lower temperatures since the conformational processes have free energies of activation nearly independent of temperature, due to the negligible contribution of the ΔS‡ values. See, for instance: Hoogosian, S, Bushweller, C. H, Anderson, W. G, Kigsley, G. J. Phys. Chem. 1976, 80, 643
    • This value can still be compared to those obtained at lower temperatures since the conformational processes have free energies of activation nearly independent of temperature, due to the negligible contribution of the ΔS‡ values. See, for instance: Hoogosian, S.; Bushweller, C. H.; Anderson, W. G.; Kigsley, G. J. Phys. Chem. 1976, 80, 643.
  • 27
    • 34047205112 scopus 로고    scopus 로고
    • -1) than the anti structure.
    • -1) than the anti structure.
  • 28
    • 33847088636 scopus 로고    scopus 로고
    • Use was made of a 60:1 molar excess of the enantiopure (R)-(-)-2,2,2-trifluoro-1-(9-anthryl)ethanol (Pirkle, W. H.; Sikkenga. D. L.; Pavlin, M. S. J. Org. Chem 1977, 42, 384).
    • Use was made of a 60:1 molar excess of the enantiopure (R)-(-)-2,2,2-trifluoro-1-(9-anthryl)ethanol (Pirkle, W. H.; Sikkenga. D. L.; Pavlin, M. S. J. Org. Chem 1977, 42, 384).
  • 29
    • 34047207312 scopus 로고    scopus 로고
    • The identity of the two ΔG‡ values measured at temperatures as different as 21 and 107 °C (for the nearly equal compounds 4 and 3, respectively) further supports the consideration that the term ΔS‡ is negligible in the majority of conformational processes, as reported in ref 11.
    • The identity of the two ΔG‡ values measured at temperatures as different as 21 and 107 °C (for the nearly equal compounds 4 and 3, respectively) further supports the consideration that the term ΔS‡ is negligible in the majority of conformational processes, as reported in ref 11.
  • 39
    • 34047218092 scopus 로고    scopus 로고
    • Use was made of the absolute shielding value reported for tetramethylsilane in the following: Foresman, J. B.; Frisch A. E. Exploring Chemistry with Electronic Structure Methods, 2nd ed. (errata corrige); Gaussian Inc.: Wallingford, CT, 1996.
    • Use was made of the absolute shielding value reported for tetramethylsilane in the following: Foresman, J. B.; Frisch A. E. Exploring Chemistry with Electronic Structure Methods, 2nd ed. (errata corrige); Gaussian Inc.: Wallingford, CT, 1996.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.