Nonplanarity in Hückel 2πAromatic Systems. An NMR-IGLO-ab Initio Proof of the Puckered Structure of Cyclobutadiene Dications

Journal of the American Chemical Society

Volumn 111, Issue 3, 1989, Pages 1147-1148

  Bremer, Matthias ^a   Ragué Schleyer, Paul Von ^a   Fleischer, Ulrich ^b  

^a UNIVERSITY OF ERLANGEN NUREMBERG   (Germany)

^b RUHR UNIVERSITY BOCHUM   (Germany)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 33845185495     PISSN: 00027863     EISSN: 15205126     Source Type: Journal    
DOI: 10.1021/ja00185a065     Document Type: Article

References (11)

1. Olah, G. A.; Bollinger, J. M.; White, A. M. J. Am. Chem. Soc. 1969, 91, 3667. (b) Olah, G. A.; Mateescu, G. P. J. Am. Chem. Soc. 1970, 92, 1430. (c) Olah, G. A.; Liang, G. J. Am. Chem. Soc. 1976, 98, 3033. (d) Olah, G. A.; Liang, G. J. Am. Chem. Soc. 1977, 99, 6045. (e) Olah, G. A.; Staral, J. S. J. Am. Chem. Soc. 1976, 98, 6290. See, also: Maier, G. Angew. Chem. 1988, 100, 317.
2. Attempts to establish the nonplanarity of cyclobutadiene dications by use of prochiral substituents were unsuccessful, see: Brendel, D. Dissertation, Erlangen, 1985.
3. See, e.g.: Pittman, C. U., Jr.; Kress, A.; Kispert, L. D. J. Org. Chem. 1974, 39, 378. Radom, L.; Schaefer, H. F., Jr. J. Am. Chem. Soc. 1977, 99, 7522.
4. Krogh-Jespersen, K.; Schleyer, P. V. R.; Pople, J. A.; Cremer, D. J. Am. Chem. Soc. 1978, 100, 4301. (b) Chandrasekhar, J.; Schleyer, P. v. R.; Krogh-Jespersen, K. J. Comput. Chem. 1981, 2, 356. (c) Krogh-Jespersen, K.; Cremer, D.; Dill, J. D.; Pople, J. A.; Schleyer, P. v. R. J. Am. Chem. Soc. 1981, 103, 2589. (d) Hess, B. A. Jr.; Ewig, C. S.; Schaad, L. J. J. Org. Chem. 1985, 50, 5809.
5. Hildenbrandt, M.; Pritzkov, H.; Zeuneck, U.; Siebert, W. Angew. Chem. 1984, 96, 371; Angew. Chem., Int. Ed. Engl. 1984, 23, 371.
6. Schleyer, P. V. R.; Budzelaar, P. H. M.; Cremer, D.; Kraka, E. Angew. Chem. 1984, 96, 374; Angew. Chem., Int. Ed. Engl. 1984, 23, 374. (b) Budzelaar, P. H. M.; Krogh-Jespersen, K.; Clark, T.; Schleyer, P. V. R. J. Am. Chem. Soc. 1985, 107, 2773. (c) Budzelaar, P. H. M.; Kraka, E.; Cremer, D.; Schleyer, P. V. R. Angew. Chem., Int. Ed. Engl. 1986, 108, 563.
7. Schindler, M. J. Am. Chem. Soc. 1987, 109, 1020.
8. Bremer, M.; Schleyer, P. V. R.; Schötz, K.; Kausch, M.; Schindler, M. Angew. Chem. 1987, 99, 795; Angew. Chem., Int. Ed. Engl. 1987, 26, 761.
9. Schleyer, P. V. R.; Laidig, K.; Wiberg, K. B.; Saunders, M.; Schindler, M. J. Am. Chem. Soc. 1988, 110, 300. (b) Laidig, K.; Saunders, M.; Wiberg, K. B.; Schleyer, P. v. R. Angew. Chem., Int. Ed. Engl. 1988, 110, 7652. (c) Koch, W.; Liu, B.; Schleyer, P. v. R., submitted for publication. (d) Schötz, K.; Fleischer, U.; Bremer, M.; Schleyer, P. v. R., to be submitted for publication.
10. 1b However, the apparent agreement is thrown into question by our data. Table II shows the chemical shift for the planar forms of these dications to be 54–68 ppm higher than the experimental values.
11. Also, see: Clark, T.; Wilhelm, D.; Schleyer, P. V. R. Tetrahedron Lett. 1982, 23, 3547.