First EPR characterisation of the structures and reactivities of α- and β-boryl radicals derived from boronic esters

Abstract

The first EPR observations of carbon-centred radicals with α- and β-boronic ester substitutents indicated moderate thermodynamic stabilisation for the former whereas the latter had an inclination towards β-scission.

References

1. D. S. Matteson, in Stereodirected Synthesis with Organoboranes, Springer, Berlin, 1995; M. Vaultier and B. Carboni in Comprehensive Organometallic Chemistry II, ed. G. Wilkinson, F. G. A. Stone and E. V. Abel, Pergamon, Oxford, 1995, vol. 11, p. 191.
2. D. S. Matteson, Organomet. Chem. Rev., 1966, 1, 1; W. G. Woods and I. S. Bengelsdorf, J. Org. Chem., 1966, 31, 2769; R. H. Fish, J. Organomet. Chem., 1972, 42, 345; N. Guennouni, C. Rassat-Deloge, B. Carboni and M. Vaultier, Synlett, 1992, 581.
3. D. S. Matteson and K. Peacock, J. Am. Chem. Soc., 1960, 82, 5759; F. Lhermitte and B. Carboni, Synlett, 1996, 377.
4. R. A. Batey, B. Pedram, K. Yong and G. Baquer, Tetrahedron Lett., 1996, 37, 6847; N. Guennouni, F. Lhermitte, S. Cochard and B. Carboni, Tetrahedron, 1995, 51, 6999.
5. J. A. Baban, V. P. J. Marti and B. P. Roberts, J. Chem. Soc., Perkin Trans 2, 1985, 1723; H. S. Dang, V. Diart, B. P. Roberts and D. A. Tocher, J. Chem. Soc., Perkin Trans. 2, 1994, 1039.
6. A. R. Lyons and M. C. R. Symons, J. Chem. Soc., Faraday Trans. 2, 1972, 68, 502.
7. M. Lucarini, G. F. Pedulli and L. Valgimigli, J. Org. Chem., 1996, 61, 4309.
8. T. J. Michnick and D. S. Matteson, Synlett, 1991, 631.
9. D. S. Matteson, R. Soundararajan, O. C. Ho and W. Gatzweiler, Organometallics, 1996, 15, 152.
10. A. J. Dobbs, B. C. Gilbert and R. O. C. Norman, J. Chem. Soc., Perkin Trans. 2, 1972, 786.
11. J. K. Kochi, Adv. Free Radical Chem., 1975, 5, 198.
12. K. U. Ingold, D. C. Nonhebel and J. C. Walton, J. Phys. Chem., 1986, 90, 2859.
13. I. Biddles, A. Hudson and J. T. Wiffen, Tetrahedron, 1972, 28, 867.
14. P. J. Krusic, P. Meakin and J. P. Jesson, J. Phys. Chem., 1971, 75, 3438.
15. J. C. Walton, Magn. Reson. Chem., 1987, 25, 998.
16. J. Heinzer, Quantum Chemistry Program Exchange, No. 209, University of Indiana, Bloomington, IN, 1972.
17. A. G. Davies and B. P. Roberts, J. Organometal. Chem., 1969, 19, P17.
18. A. G. Davies and B. P. Roberts, J. Chem. Soc., Chem. Commun., 1969, 699.
19. P. J. Krusic and J. K. Kochi, J. Am. Chem. Soc., 1969, 91, 3942.
20. D. S. Matteson, Progress in Boron Chemistry, ed. R. J. Brotherton and H. Steinberg, Pergamon, Oxford, 1970, vol. 3, p 117.
21. B. M. Mikhailov and M. E. Nikolaeva, Izv. Akad. Nauk. SSSR, Ser. Khim., 1963, 1368 (Chem. Abstr., 59, 15296f).