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Volumn 72, Issue 26, 2007, Pages 10088-10095

Retro-Diels-Alder reaction of 4H-1,2-benzoxazines to generate o-quinone methides: Involvement of highly polarized transition states

Author keywords

[No Author keywords available]

Indexed keywords

BENZENE; DENSITY FUNCTIONAL THEORY; HALOGEN COMPOUNDS; REACTION KINETICS; THERMAL EFFECTS;

EID: 37549050595     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo702246w     Document Type: Article
Times cited : (38)

References (63)
  • 11
    • 0000430022 scopus 로고    scopus 로고
    • For recent reports on 4H-1,2-benzoxazines, see: (a) Ohwada, T.; Ohta, T.; Shudo, K. Tetrahedron 1987, 43, 297-305.
    • For recent reports on 4H-1,2-benzoxazines, see: (a) Ohwada, T.; Ohta, T.; Shudo, K. Tetrahedron 1987, 43, 297-305.
  • 24
    • 0001298716 scopus 로고
    • For recent reports on the use of o-quinone methides, see: a
    • For recent reports on the use of o-quinone methides, see: (a) Adam, W.; Hadjiarapoglou, L.; Peters, K.; Sauter, M. J. Am. Chem. Soc. 1993, 115, 8603-8608.
    • (1993) J. Am. Chem. Soc , vol.115 , pp. 8603-8608
    • Adam, W.1    Hadjiarapoglou, L.2    Peters, K.3    Sauter, M.4
  • 42
    • 37549037439 scopus 로고    scopus 로고
    • Griesbeck, A. G, Ed, Houben-Weyl: New York, Chapter 12, pp
    • (b) Pettus, T. R. R.; Selenski, C.; Griesbeck, A. G. In Science of Synthesis; Griesbeck, A. G., Ed.; Houben-Weyl: New York, 2006; Chapter 12, pp 831-899.
    • (2006) Science of Synthesis , pp. 831-899
    • Pettus, T.R.R.1    Selenski, C.2    Griesbeck, A.G.3
  • 52
    • 0002375666 scopus 로고    scopus 로고
    • Retro-Diels-Alder reaction of isomeric benzoxazine was reported: Glover, S. A.; Jones, K. M.; McNee, I. R.; Rowbottom, C. A. J. Chem. Soc., Perkin Trans. 2 1996, 1367-1376.
    • Retro-Diels-Alder reaction of isomeric benzoxazine was reported: Glover, S. A.; Jones, K. M.; McNee, I. R.; Rowbottom, C. A. J. Chem. Soc., Perkin Trans. 2 1996, 1367-1376.
  • 53
    • 37549061729 scopus 로고    scopus 로고
    • While probably due to the shallow potential energy surface, it was difficult to find the transition structure for the homolytic cleavage of the N-O bond of 1a; we obtained the biradical structure of 1a in UB3LYP/ 6-31 +G(d,p) calculations, which involved homolytic cleavage of the N-O bond. Formation of the biradical intermediate was endothermic, and the energy difference from 1a is 39.6 kcal/mol (UB3LYP/6-311+G(d,p)// UB3LYP/6-31+G(d,p, This result suggests that the activation energy for the putative biradical formation process, the rate-determining step in the singlet biradical pathway, will be highly energetic as compared with the asynchronous concerted process (30.0 kcal/mol, B3LYP/6-311+G(d,p)// B3LYP/6-31+Gd,p, see Figure S4, Supporting Information
    • While probably due to the shallow potential energy surface, it was difficult to find the transition structure for the homolytic cleavage of the N-O bond of 1a; we obtained the biradical structure of 1a in UB3LYP/ 6-31 +G(d,p) calculations, which involved homolytic cleavage of the N-O bond. Formation of the biradical intermediate was endothermic, and the energy difference from 1a is 39.6 kcal/mol (UB3LYP/6-311+G(d,p)// UB3LYP/6-31+G(d,p)). This result suggests that the activation energy for the putative biradical formation process, the rate-determining step in the singlet biradical pathway, will be highly energetic as compared with the asynchronous concerted process (30.0 kcal/mol, B3LYP/6-311+G(d,p)// B3LYP/6-31+G(d,p)) (see Figure S4, Supporting Information).
  • 56
    • 37549029705 scopus 로고    scopus 로고
    • 5 was not able to be prepared.
    • 5 was not able to be prepared.
  • 57
    • 37549066288 scopus 로고    scopus 로고
    • 2 σ*-orbital (see Table S3 and Figure S5 in the Supporting Information).
    • 2 σ*-orbital (see Table S3 and Figure S5 in the Supporting Information).
  • 58
    • 37549060991 scopus 로고    scopus 로고
    • Acceleration of the retro-Diels-Alder reaction of 4H-1,2- benzoxazine bearing CF3 at C8 (1l) might be related to the fact that the negative charge of N2 in the reactant 1l, 0.043) is the smallest among the isomers (1g and 1j-l, see Table S2, Supporting Information, This small negative charge of N2 of 1l can be interpreted in terms of the inductive effect of CF3 at C8, which polarizes the electron density of the O1-N2 bond toward the O1 atom. Consequently, the electron-deficient N2 promotes redistribution of the electrons of the C3-C4 bond into the N2-C3 bond (Figure 6, The NPA charge also showed the negative charge of C4 was the highest in 1j among the isomers bearing CF3 at C5 (1j, C6 1k
    • 5 (1j) showed the smallest reaction rate among the isomers (1g and 1j-l) (Table 5).
  • 59
    • 37549061375 scopus 로고    scopus 로고
    • 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; Gaussian, Inc.; Pittsburgh, PA, 2003.


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