Competing pathways in the [2 + 2] cycloadditions of cyclopentyne and benzyne. A DFT and ab initio study

Journal of Organic Chemistry

Volumn 69, Issue 16, 2004, Pages 5390-5394

  Ozkan, Ilker ^a   Kinal, Armagan ^a  

^a MIDDLE EAST TECHNICAL UNIVERSITY   (Turkey)

Author keywords

[No Author keywords available]

Indexed keywords

ADDITION REACTIONS; ETHYLENE; FREE RADICALS; PROBABILITY DENSITY FUNCTION; STEREOCHEMISTRY;

CYCLOADDITIONS; CYCLOPENTYNE;

BENZENE;

BENZENE DERIVATIVE; BENZYNE; CYCLOPENTYNE; ETHYLENE; UNCLASSIFIED DRUG;

ARTICLE; CALCULATION; CYCLOADDITION; ENERGY; REACTION ANALYSIS; STEREOCHEMISTRY; STRUCTURE ANALYSIS; THEORETICAL MODEL;

EID: 3542997453     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo049542f     Document Type: Article

References (37)

1. (a) Fitjer, L.; Modaressi, S. Tetrahedron Lett. 1983, 24, 5495.
2. (b) Gilbert, J. C.; Baze, M. E. J. Am. Chem. Soc. 1984, 106, 1885.
3. (a) Woodward, R. B.; Hoffmann, R. J. Am. Chem. Soc. 1965, 87, 395.
4. (b) Woodward, R. B.; Hoffmann, R. J. Am. Chem. Soc. 1965, 87, 2046.
5. a] cycloaddition of acetylene and ethylene (Hess, B. A.; Schaad, L. J.; Reinhoudt, D. N. Int. J. Quantum Chem. 1986, 29, 345). We repeated their calculations and found that the stationary point reported by these authors is actually a second order saddle point. The concerted path for [2 + 2] cycloadditions probably does not exist at all. See also: Bernardi, F.; Bottoni, A.; Olivucci, M.; Robb, M. A.; Schlegel, H. B.; Tonachini, G. J. Am. Chem. Soc. 1988, 110, 5993.
6. a] cycloaddition of acetylene and ethylene (Hess, B. A.; Schaad, L. J.; Reinhoudt, D. N. Int. J. Quantum Chem. 1986, 29, 345). We repeated their calculations and found that the stationary point reported by these authors is actually a second order saddle point. The concerted path for [2 + 2] cycloadditions probably does not exist at all. See also: Bernardi, F.; Bottoni, A.; Olivucci, M.; Robb, M. A.; Schlegel, H. B.; Tonachini, G. J. Am. Chem. Soc. 1988, 110, 5993.
7. (a) Laird, D. W.; Gilbert, J. C. J. Am. Chem. Soc. 2091, 123, 6704.
8. (b) Bachrach, S. M.; Gilbert, J. C.; Laird, D. W. J. Am. Chem. Soc. 2001, 123, 6706.
9. (c) Gilbert, J. C.; Hou, D. J. Org. Chem. 2003, 68, 10067.
10. The following mnemonics are used throughout this paper. a: alkyne, b: biradical, c: carbene, p: product. Transition structures are labeled by combining the letter codes of the associated PES minima.
11. (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648.
12. (b) Lee, C.; Yang, W.; Parr, R. G. Phys. Rev B 1988, 37, 785.
13. Olivella, S.; Pericas, M. A.; Riera, A.; Sole, A. J. Chem. Soc., Perkin Trans. 2 1986, 613.
14. Concerned with the highly strained nature of the two cycloalkynes reported herein, we have explored Scheme 1 for the simplest open-chain alkyne system; namely, cycloaddition of acetylene with ethylene. All species of Scheme 1 are also present in the latter system. The free energy profiles of the species in the acetylene system are presented in Figure S1 of the Supporting Information.
15. Jones, M.; Levin, R. H. J. Am. Chem. Soc. 1969, 91, 6411.
16. (a) Goldstein, E.; Beno, B.; Houk, K. N. J. Am. Chem. Soc. 1996, 118, 6036.
17. (b) Houk, K. N.; Beno, B. R.; Nendel, M.; Black, K.; Yoo, H. Y.; Wilsey, S.; Lee, J. K. THEOCHEM 1997, 398-399, 169.
18. (c) Hrovat, D. A.; Beno, B. R.; Lange, H.; Yoo, H. Y.; Houk, K. N.; Borden, W. T. J. Am. Chem. Soc. 2000, 122, 7456.
19. The active orbitals were the in-plane and out-of-plane (π, π*) orbitals of the triple bond in the alkyne plus (π, π*) orbitals of the alkene. They correlate with the (π, π*), and (σ,σ*) orbitals of the C2-C3 and C1-C4 bonds of p (see Scheme 1 for the numbering).
20. McDouall, J. J.; Peasley, K.; Robb, M. A. Chem. Phys. Lett. 1988, 148, 183.
21. Frisch, M. J.; Trucks, 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 (Rev. A.9), Gaussian, Inc., Pittsburgh, PA, 1998.
22. Schmidt, M. W.; Baldridge, K. K.; Boatz, J. A.; Elbert, S. T.; Gordon, M. S.; Jensen, J. H.; Koseki, S.; Matsunaga, N.; Nguyen, K. A.; Su, S.; Windus, T. L.; Dupuis, M.; Montgomery, J. A. J. Comput. Chem. 1993, 14, 1347.
23. (a) Ishida, K.; Morokuma, K.; Komornicki, A. J. Chem. Phys. 1977, 66, 2153.
24. (b) Fukui, K. Acc. Chem. Res. 1981, 14, 363.
25. Ball and stick models with selected geometric parameters of all stationary structures in this work are available in the Supporting Information.
26. s symmetry, but the symmetry plane contains the ethylenic double bond instead of being perpendicular to it. Further, bond formation is concerted but asynchronous. See, for example: (a) Apeloig, Y.; Karni, M.; Stang, P. J.; Fox, D. P. J. Am. Chem. Soc. 1983, 105, 4781.
27. (b) Zurawski, B.; Kutzelnigg, W. J. Am. Chem. Soc. 1978, 100, 2654.
28. Adamo, C.; Barone, V. J. Chem. Phys. 1998, 108, 664.
29. (a) Perdew, J. P.; Chevary, J. A.; Vosko, S. H.; Jackson, K. A.; Pederson, M. R.; Singh, D. J.; Fiolhais, C. Phys. Rev. B 1992, 46, 6671.
30. (b) Perdew, J. P.; Burke, K.; Wang, Y. Phys. Rev. B 1996, 54, 16533.
31. Occupation number of the CASSCF natural orbital corresponding to the LUMO is used here as a measure of biradical character. For a discussion of biradical character in open-shell singlets, see, for example: Ozkan, I.; Kinal A.; Balci, M. J. Phys. Chem. A 2004, 108, 507 and references therein.
32. 2〉 = 0.3).
33. Due to the biradical species, proximity of the triplet surface and, therefore, the possibility of intersystem crossing is a concern. We optimized the triplet states of both systems at UB3LYP/6-311G(d,p) level. The triplet minimum is nearly isoenergetic with the singlet biradical b in both systems (geometries are also similar; see the Supporting Information). Single point CAS(6,6)/6-31G* calculations support the DFT results suggesting that DFT singlet and triplet energies of the biradicals are trustworthy. This minimum is most likely the global one in the region of the triplet surface covering the species involved in Scheme 1. Further, the triplet surface is higher than the singlet elsewhere in Scheme 1. We believe intersystem crossing is not operative in the cycloaddition.
34. Due to the flat nature of PES in the region of biradical species it is not easy to discern the isomerization TS from bp‡. This was less of a problem with CASSCF than it was with DFT. The barriers involved are definitely small (0-2 kcal/mol), but their precise magnitudes cannot be predicted by the present methods.
35. There seems to be less competition between rotation and cyclization in 1b since the barriers are 0.5 and 1.8 kcal/mol, respectively.
36. Kitamura, T.; Kotani, M.; Yokoyama, T.; Fujiwara, Y. J. Org. Chem. 1999, 64, 680.
37. Johnson, R. P.; Daoust, K. J. J. Am. Chem. Soc. 1995, 117, 362.