Stannanes as free-radical reducing agents: an ab initio study of hydrogen atom transfer from some trialkyltin hydrides to alkyl radicals

Abstract

Ab initio molecular orbital calculations using a (valence) double-ξ pseudopotential (DZP) basis set, with (MP2, QCISD) and without (SCF) the inclusion of electron correlation, predict that hydrogen atoms, methyl, ethyl, isopropyl and tert-butyl radicals abstract hydrogen atoms from stannane and trimethyltin hydride via transition states in which the attacking and leaving radicals adopt a colinear arrangement. Transition states in which (overall) Sn–C separations of 3.50 Å have been calculated; these distances appear to be independent of the nature of the attacking radical and alkyl substitution at tin. At the highest level of theory (QCISD/DZP//MP2/DZP), energy barriers (ωE₁^‡) of 18–34 kJ mol^-1 are predicted for the forward reactions, while the reverse reactions (ωE₂^‡) are calculated to require 140–170 kJ mol^-1. These values are marginally affected by the inclusion of zero-point vibrational energy correction. Importantly, QCISD and MP2 calculations predict correctly the relative order of radical reactivity toward reduction by stannanes: tert-butyl > isopropyl > ethyl. By comparison, SCF/DZP, AM1 and AM1(CI = 2) calculations perform somewhat more poorly in their prediction of relative radical reactivity.

References

1. B. Giese, Radicals in Organic Synthesis: Formation of Carbon-Carbon Bonds, Pergamon Press, Oxford, 1986.
2. W. P. Neumann, Synthesis, 1987, 665; D. P. Curran, Synthesis, 1988, 417, 489; C. P. Jasperse, D. P. Curran and T. L. Fevig, Chem. Rev., 1991, 91, 1237.
3. For some examples of other synthetically useful stannanes, see: U. Gerigk, M. Gerlach, W. P. Neumann, R. Vieler and V. Weintritt, Synthesis, 1990, 448; J. Light and R. Breslow, Tetrahedron Lett., 1990, 31, 2957; F. Ferkous, D. Messadi, B. De Jeso, M. Degueil-Castaing and B. Maillard, J. Organomet. Chem., 1991, 420, 315; W. P. Neumann and M. Peterseim, React. Polym., 1993, 20, 189; D. P. Curran and S. Hadida, J. Am. Chem. Soc., 1996, 118, 2531; D. P. Curran and D. Nanni, Tetrahedron: Asymmetry, 1996, 7, 2417.
4. C. H. Schiesser and L. M. Wild, Tetrahedron, 1996, 52, 13 265 and references cited therein.
5. D. J. Carlsson and K. U. Ingold, J. Am. Chem. Soc., 1968, 90, 1055; D. J. Carlsson and K. U. Ingold, J. Am. Chem. Soc., 1968, 90, 7047; M. Newcomb, Tetrahedron, 1993, 49, 1151; D. V. Avila, K. U. Ingold, J. Lusztyk, W. R. Dolbier, Jr., H.-Q. Pan and M. Muir, J. Am. Chem. Soc., 1994, 116, 99; S. J. Garden, D. V. Avila, A. L. J. Beckwith, V. W. Bowry, K. U. Ingold and J. Lusztyk, J. Org. Chem., 1996, 61, 805.
6. L. J. Johnston, J. Lusztyk, D. D. M. Wayner, A. N. Abeywickrema, A. L. J. Beckwith, J. C. Scaiano and K. U. Ingold, J. Am. Chem. Soc., 1985, 107, 4594.
7. C. Chatgilialoglu, K. U. Ingold and J. C. Scaiano, J. Am. Chem. Soc., 1981, 103, 7739.
8. O. M. Musa, J. H. Horner, H. Shahin and M. Newcomb, J. Am. Chem. Soc., 1996, 118, 3862.
9. J. Lusztyk, B. Maillard and K. U. Ingold, J. Org. Chem., 1986, 51, 2457; M. Newcomb and S. U. Park, J. Am. Chem. Soc., 1986, 108, 4132; C. Chatgilialoglu, Acc. Chem. Res., 1992, 25, 188; C. Chatgilialoglu, A. Guerrini and M. Lucarini, J. Org. Chem., 1992, 57, 3405; C. Chatgilialoglu, C. Ferreri and M. Lucarini, J. Org. Chem., 1993, 58, 249.
10. C. Chatgilialoglu, D. Griller and M. Lasage, J. Org. Chem., 1988, 53, 3641; M. Ballestri, C. Chatgilialoglu, K. B. Clark, D. Griller, B. Giese and B. Kopping, J. Org. Chem., 1991, 56, 678.
11. J. Lusztyk, B. Maillard, D. A. Lindsay and K. U. Ingold, J. Am. Chem. Soc., 1983, 105, 3578; J. Lusztyk, B. Maillard, S. Deycard, D. A. Lindsay and K. U. Ingold, J. Org. Chem., 1987, 52, 3509.
12. C. H. Schiesser, B. A. Smart and T.-A. Tran, Tetrahedron, 1995, 51, 3327; C. H. Schiesser and B. A. Smart, Tetrahedron, 1995, 51, 6051 see correction in: C. H. Schiesser, B. A. Smart and T.-A. Tran, Tetrahedron, 1995, 51, 10 651 For performance of DZP basis set see: B. A. Smart and C. H. Schiesser, J. Comput. Chem., 1995, 16, 1055.
13. C. H. Schiesser and M. A. Skidmore, Chem. Commun., 1996, 1419.
14. A. L. J. Beckwith and A. A. Zavitsas, J. Am. Chem. Soc., 1995, 117, 607.
15. M. J. Frisch, G. W. Trucks, M. Head-Gordon, P. M. W. Gill, M. W. Wong, J. B. Foresman, B. G. Johnson, H. B. Schlegel, M. A. Robb, E. S. Replogle, R. Gomperts, J. L. Andres, K. Raghavachari, J. S. Binkley, C. Gonzales, R. L. Martin, D. J. Fox, D. J. Defrees, J. Baker, J. J. P. Stewart and J. A. Pople, GAUSSIAN 92, Revision F, Gaussian Inc., Pittsburgh, PA, 1992.
16. M. J. Frisch, G. W. Trucks, H. B. Schlegel, P. M. W. Gill, B. G. Johnson, M. A. Robb, J. R. Cheeseman, T. Keith, G. A. Petersson, J. A. Montgomery, K. Raghavachari, M. A. Al-Laham, V. G. Zakrzewski, J. V. Ortiz, J. B. Foresman, C. Y. Peng, P. Y. Ayala, W. Chen, M. W. Wong, J. L. Andres, E. S. Replogle, R. Gomperts, R. L. Martin, D. J. Fox, J. S. Binkley, D. J. Defrees, J. Baker, J. J. P. Stewart, M. Head-Gordon, C. Gonzalez and J. A. Pople, GAUSSIAN 94, Revision B.3, Gaussian Inc., Pittsburgh, PA, 1995.
17. W. J. Hehre, L. Radom, P. v. R. Schleyer and P. A. Pople, Ab Initio Molecular Orbital Theory, Wiley, New York, 1986.
18. AMPAC 5.0, © 1994 Semichem, 7128 Summitt, Shawnee, KS 66216.
19. C. H. Schiesser, M. L. Styles and L. M. Wild, J. Chem. Soc., Perkin Trans. 2, 1996, 2257.