Kinetics of strain-activated intramolecular Diels-Alder reactions between furan and bicyclopropylidene as well as methylenecyclopropane moieties
Buback, M., Heiner, T., Hermans, B., Kowollik, C., Kozhushkov, S. I., & De Meijere, A. (1998) Kinetics of strain-activated intramolecular Diels-Alder reactions between furan and bicyclopropylidene as well as methylenecyclopropane moieties. European Journal of Organic Chemistry.
The intramolecular Diels-Alder reactions of the furans 1a, 1b, 3a and 3b in dichloromethane solution at pressures up to 3 kbar have been studied by quantitative on-line FT-IR spectroscopy. At identical pressure and temperature cyclization rates are significantly faster, by a factor of 8.1 and 6.8, for the b-type species of 1 and 3, respectively. The activation enthalpies of the four cyclizations are very similar, between 78.5 ± 0.6 and 82.5 ± 2.7 kJ mol-1. The activation volumes, ΔV0 ≠, are in the range -28.4 ± 1.3 (1a) to -40.8 ± 2.0 cm3 mol-1 (3b). These data show that intramolecular Diels-Alder reactions are not necessarily associated with less negative activation volumes than intermolecular Diels-Alder reactions. The size of ΔV0 ≠, however, appears to be clearly correlated with the type and the position of substituents at the diene or dienophile moieties. Replacement of the H atom on the furan ring by the methoxy group turns ΔV0 ≠ more negative by 7.4 ± 2.9 cm3 mol-1 for 1a and 1b and by 8.1 ± 2.0 cm3 mol-1 for 3a and 3b. Varying the dienophile moiety from methylenecyclopropane to bicyclopropylidene lowers ΔV0 ≠ by about 3.5 cm3 mol-1 between 1a and 3a and by about 5.0 cm3 mol-1 between 1b and 3b, which demonstrates the larger steric hindrance due to the tetrasubstitution of the double bond. Comparing the effects on cyclization rate associated with having either one or two cyclopropane units at the dienophile double bond suggests that the rate enhancing influence of strain energy slightly overcompensates a reduction in rate that is expected to go with the increased steric hindrance due to the second cyclopropane unit.
Impact and interest:
Citation counts are sourced monthly from and citation databases.
These databases contain citations from different subsets of available publications and different time periods and thus the citation count from each is usually different. Some works are not in either database and no count is displayed. Scopus includes citations from articles published in 1996 onwards, and Web of Science® generally from 1980 onwards.
Citations counts from theindexing service can be viewed at the linked Google Scholar™ search.
|Item Type:||Journal Article|
|Additional Information:||Cited By :7
Export Date: 20 September 2016
Correspondence Address: Buback, M.; Inst. für Physikalische Chemie, Georg-August-Univ. Göttingen, Tammannstraße 6, D-37077 Göttingen, Germany
References: Keay, A., Dibble, P.W., (1989) Tetrahedron Lett., 30, pp. 1045-1046; Ferroud, C., Revial, G., D'Anfelo, J., (1985) Tetrahedron Lett., 26, pp. 3981-3984; Burell, S.J., Derome, A.E., Edenborough, M.S., Harwood, L.M., Leeming, S.A., Isaacs, N.S., (1985) Tetrahedron Lett., 26, pp. 2229-2232; Isaacs, N.S., Beeke, P.V.V.D., (1982) Tetrahedron Lett., 23, pp. 2147-2149; Buback, M., Gerke, K., Ott, C., Tietze, L.F., (1994) Chem. Ber., 127, pp. 2241-2248; Diedrich, M.K., Hochstrate, D., Klärner, F.G., Zimny, B., (1994) Angew. Chem, 106, pp. 1135-1137; (1994) Angew. Chem. Int. Ed. Engl., 33, pp. 1079-1081; Heiner, T., Kozhushkov, S.I., Noltemeyer, M., Haumann, T., Boese, R., De Meijere, A., (1996) Tetrahedron, 52, pp. 12185-12196; Heiner, T., Michalski, S., Gerke, K., Kuchta, G., De Meijere, A., Buback, M., (1995) Synlett, pp. 355-357; Antonioletti, R., D'Auria, M., Mico, A.D., Piancatelli, G., Scetti, A., (1984) Synthesis, pp. 280-281; Heiner, T., (1996), Dissertation, Universität GöttingenPress, W.H., Flarnmery, B.P., Teukolsky, S.A., Vetterling, W.T., (1989) Numerical Recipes, , Cambridge University Press, Cambridge; Asano, T., Okada, T., (1984) J. Phys. Chem., 88, pp. 238-243; El'yanov, B.S., Gonikberg, E.M., (1979) J. Chem. Soc., Farad. Trans., 15, pp. 172-191; Niklaus, A., (1996), Dissertation, Universität GöttingenJenner, G., (1975) Angew, Chem., 87, pp. 186-194; (1975) Angew. Chem. Int. Ed. Engl., 14, pp. 137-143; Isaacs, N.S., Beeke, P.V.V.D., (1982) Tetrahedron Lett., 23, pp. 2147-2149; Le Noble, W.J., (1983) Chem. Unserer Zeit, 5, pp. 152-162; Buback, M., Hinton, C., (1996) High Pressure Techniques in Chemistry and Physics: A Practical Approach, p. 51. , (Eds.: W. B. Holzapfel, N. S. Isaacs), Oxford University Press, Oxford
|Keywords:||Activation parameters, Cycloadditions, intramolecular, [4 + 2], High-pressure chemistry, Polycycles, Small ring systems, Strain activation, Volume profile|
|Divisions:||Current > Schools > School of Chemistry, Physics & Mechanical Engineering
Current > Institutes > Institute for Future Environments
Current > QUT Faculties and Divisions > Science & Engineering Faculty
|Deposited On:||22 Sep 2016 04:50|
|Last Modified:||22 Sep 2016 04:50|
Repository Staff Only: item control page