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Volumn 74, Issue 1, 2009, Pages 351-358

Experimental and DFT studies on competitive heterocyclic rearrangements. 3. A cascade isoxazole-1,2,4-oxadiazole-oxazole rearrangement

Author keywords

[No Author keywords available]

Indexed keywords

COMPUTATIONAL DATUMS; DFT STUDIES; ISOXAZOLE; ISOXAZOLES; NEUTRAL CONDITIONS; NUCLEOPHILIC ATTACKS; OXADIAZOLE; OXADIAZOLES; OXAZOLE; OXAZOLES; REACTION TEMPERATURES; RING CONTRACTIONS; RING EXPANSIONS;

EID: 58149314192     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo802081k     Document Type: Article
Times cited : (34)

References (56)
  • 6
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    • See also specific classes of ring transformations reviewed in: (e) Comprehensive Heterocyclic Chemistry; Katritzky, A. R., Rees, C. W., Eds.; Pergamon Press: Oxford, 1984; Vols. 1-8.
    • See also specific classes of ring transformations reviewed in: (e) Comprehensive Heterocyclic Chemistry; Katritzky, A. R., Rees, C. W., Eds.; Pergamon Press: Oxford, 1984; Vols. 1-8.
  • 7
    • 0003607021 scopus 로고    scopus 로고
    • Katritzky, A. R, Rees, C. W, Scriven, E. F. V, Eds, Elsevier: Amsterdam, Vols
    • (f) Comprehensive Heterocyclic Chemistry II; Katritzky, A. R., Rees, C. W., Scriven, E. F. V., Eds.; Elsevier: Amsterdam, 1996; Vols. 1-9.
    • (1996) Comprehensive Heterocyclic Chemistry II , vol.1-9
  • 10
    • 0032583495 scopus 로고    scopus 로고
    • Moreover, for DFT studies on bicyclic BK rearrangements, see, for example: (b) Eckert, F.; Rauhut, G. J. Am. Chem. Soc. 1998, 120, 13478-13484,
    • Moreover, for DFT studies on bicyclic BK rearrangements, see, for example: (b) Eckert, F.; Rauhut, G. J. Am. Chem. Soc. 1998, 120, 13478-13484,
  • 11
    • 0035838891 scopus 로고    scopus 로고
    • (c) Rauhut, G. J. Org. Chem. 2001, 66, 5444-5448.
    • (2001) J. Org. Chem , vol.66 , pp. 5444-5448
    • Rauhut, G.1
  • 15
    • 58149311566 scopus 로고    scopus 로고
    • Since in the RCRE route the endocyclic N(4) ring nitrogen is involved in the formation of the diazirine, we named such intermediate as diazirine-endo. For the same reason, we named the first MNAC intermediate as diazirine-exo, since the exocyclic side-chain nitrogen is involved in its formation.
    • Since in the RCRE route the endocyclic N(4) ring nitrogen is involved in the formation of the diazirine, we named such intermediate as diazirine-endo. For the same reason, we named the first MNAC intermediate as diazirine-exo, since the exocyclic side-chain nitrogen is involved in its formation.
  • 30
    • 58149303360 scopus 로고    scopus 로고
    • This choice also allows an easier comparison with previously calculated data for similar reactions such as photoinduced MNAC and RCRE in MeOH (see ref 5) and thermal BK, MNAC, and RCRE in DMSO see ref 6
    • This choice also allows an easier comparison with previously calculated data for similar reactions such as photoinduced MNAC and RCRE in MeOH (see ref 5) and thermal BK, MNAC, and RCRE in DMSO (see ref 6).
  • 31
    • 58149288729 scopus 로고    scopus 로고
    • -, and previously studied 3-acylamino-1,2,4-oxadiazoles is given in the Supporting Information.
    • -, and previously studied 3-acylamino-1,2,4-oxadiazoles is given in the Supporting Information.
  • 33
    • 58149308908 scopus 로고    scopus 로고
    • 6 at the temperature reachable with the instrument. Analytical and preparative TLC were repeatedly eluted in a light petroleum ether/ ethyl acetate 5/1 mixture to achieve satisfactory separation of the two compounds.
    • 6 at the temperature reachable with the instrument. Analytical and preparative TLC were repeatedly eluted in a light petroleum ether/ ethyl acetate 5/1 (vol/vol) mixture to achieve satisfactory separation of the two compounds.
  • 34
    • 58149303361 scopus 로고    scopus 로고
    • The previously reported yields of oxazoles 8a and 8b (see also ref 10) were reproduced, within experimental error, after compounds 1a and 1b were heated for 4 h at 110°C in DMF/t-BuOK.
    • The previously reported yields of oxazoles 8a and 8b (see also ref 10) were reproduced, within experimental error, after compounds 1a and 1b were heated for 4 h at 110°C in DMF/t-BuOK.
  • 35
    • 0015741048 scopus 로고    scopus 로고
    • In the benzo-condensed series, the formation of 1,2,4-oxadiazoles was reported from a base-catalyzed BK rearrangement of 3-acylaminobenzisoxazoles. Harsányi, K. J. Heterocycl. Chem. 1973, 10, 957-961
    • In the benzo-condensed series, the formation of 1,2,4-oxadiazoles was reported from a base-catalyzed BK rearrangement of 3-acylaminobenzisoxazoles. Harsányi, K. J. Heterocycl. Chem. 1973, 10, 957-961.
  • 37
    • 58149290316 scopus 로고    scopus 로고
    • The higher temperature reached in refluxing ethanol allowed an easier overtake of the activation barriers of both BK (of 1a- and 5a, and MNAC (of 5a, rearrangements, with respect to the reaction carried out in methanol. Moreover, in a previous report see ref 10, no reaction was observed when 1a was refluxed in ethanol/KOH medium
    • -) rearrangements, with respect to the reaction carried out in methanol. Moreover, in a previous report (see ref 10), no reaction was observed when 1a was refluxed in ethanol/KOH medium.
  • 38
    • 37049147162 scopus 로고    scopus 로고
    • The intramolecular reaction between the isoxazole nucleus (neutral substrate) and the side-chain oxygen (anionic nucleophile) occurs through a transition state with charge dispersion. Therefore, the solvent stabilization effect is more pronounced for the reagent than for the transition state and the activation barrier increases with solvent polarity. See: (a) Hughes, E. D.; Ingold, C. K. J. Chem. Soc. 1935, 244-255.
    • The intramolecular reaction between the isoxazole nucleus (neutral substrate) and the side-chain oxygen (anionic nucleophile) occurs through a transition state with charge dispersion. Therefore, the solvent stabilization effect is more pronounced for the reagent than for the transition state and the activation barrier increases with solvent polarity. See: (a) Hughes, E. D.; Ingold, C. K. J. Chem. Soc. 1935, 244-255.
  • 41
    • 58149294102 scopus 로고    scopus 로고
    • In a previous report ref 10, no reaction was observed by either refluxing 1a in DMF for 4 h or keeping it in the melted phase at 170°C for 30 min
    • In a previous report (ref 10), no reaction was observed by either refluxing 1a in DMF for 4 h or keeping it in the melted phase at 170°C for 30 min.
  • 43
  • 44
    • 58149294100 scopus 로고    scopus 로고
    • Standard free energy values of compound 5d, calculated at 298.15 K and relative to compound 1d, are ΔG° = 15.0 kJ/mol (in vacuo), ΔG° = 15.4 kJ/mol (in DMSO), and ΔG° = 13.5 kJ/mol (in MeOH). The standard free energy value calculated at the B3LYP/6-31++G(d,p) level is-572.04948 au for 1d; the solvation free energy values for 1d are -4.65 kcal/mol (in DMSO) and -11.92 kcal/mol (in MeOH).
    • Standard free energy values of compound 5d, calculated at 298.15 K and relative to compound 1d, are ΔG° = 15.0 kJ/mol (in vacuo), ΔG° = 15.4 kJ/mol (in DMSO), and ΔG° = 13.5 kJ/mol (in MeOH). The standard free energy value calculated at the B3LYP/6-31++G(d,p) level is-572.04948 au for 1d; the solvation free energy values for 1d are -4.65 kcal/mol (in DMSO) and -11.92 kcal/mol (in MeOH).
  • 56
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    • Frisch, M. J, Tracks, G. W, Schlegel, H. B, Scuseria, G. E, Robb, M. A, Cheeseman, J. R, Zakrzewski, V. G, Montgomery, J. A, Jr, Stratmann, R. E, Burant, J. C, Dapprich, S, Millam, J. M, Daniels, A. D, Kudin, K. N, Strain, M. C, Farkas, O, Tomasi, J, Barone, V, Cossi, M, Cammi, R, Mennucci, B, Pomelli, C, Adamo, C, Clifford, S, Ochterski, J, Petersson, G. A, Ayala, P. Y, Cui, Q, Morokuma, K, Malick, D. K, Rabuck, A. D, Raghavachari, K, Foresman, J. B, Cioslowski, J, Ortiz, J. V, Baboul, A. G, Stefanov, B. B, Liu, G, Liashenko, A, Piskorz, P, Komaromi, I, Gomperts, R, 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, Andres, J. L, Gonzalez, C, Head-Gordon, M, Replogle, E. S, Pople, J. A. Gaussian 98, revision A.8; Gaussian, Inc, Pittsburgh, PA, 1998
    • Frisch, M. J.; Tracks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Zakrzewski, V. G.; Montgomery, J. A., Jr.; Stratmann, R. E.; Burant, J. C.; Dapprich, S.; Millam, J. M.; Daniels, A. D.; Kudin, K. N.; Strain, M. C.; Farkas, O.; Tomasi, J.; Barone, V.; Cossi, M.; Cammi, R.; Mennucci, B.; Pomelli, C.; Adamo, C.; Clifford, S.; Ochterski, J.; Petersson, G. A.; Ayala, P. Y.; Cui, Q.; Morokuma, K.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.; Cioslowski, J.; Ortiz, J. V.; Baboul, A. G.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.; Gomperts, R.; 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.; Andres, J. L.; Gonzalez, C.; Head-Gordon, M.; Replogle, E. S.; Pople, J. A. Gaussian 98, revision A.8; Gaussian, Inc.: Pittsburgh, PA, 1998.


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