TY - JOUR
T1 - Homolytic Reactions of Homocubane and Basketane
T2 - Rearrangement of the 9-Basketyl Radical by Multiple β-Scissions
AU - Binmore, Gavin T.
AU - Walton, John C.
AU - Delia, Ernest W.
AU - Elsey, Gordon M.
AU - Head, Nicholas J.
PY - 1994/4/1
Y1 - 1994/4/1
N2 - Methods are described for the synthesis of 9-hydroxy-and 9-bromopentacyclo[4.3.0.02, 5.03, 8.04, 7]nonane (homocubane derivatives) and for the same derivatives of pentacyclo[4.3.0.02, 5.03, 8.04, 7]decane (basketane). The 9-homocubyl and 9-basketyl radicals generated from these precursors were observed by EPR spectroscopy. In spite of their very large strain energies, both radicals rearranged extremely slowly, and unrearranged products were obtained from homolytic reactions in solution at temperatures below 150 °C. At higher temperatures the 9-basketyl radical rearranged by a cascade of three β-scissions, the ultimate product being 1 -(4-cyclobut-2-enyl)cyclohexa-2, 4-diene. The Arrhenius parameters for the rearrangement were found to be log(Ar/s-1) = 13.6, Er= 13.5 kcal mob-1. The 9-homocubyl radical did not rearrange even at 220 °C. An explanation as to why these cage radicals rearrange at least 6 orders of magnitude more slowly than the related cubylcarbinyl radical is presented, and semiempirical SCF-MO calculations are reported.
AB - Methods are described for the synthesis of 9-hydroxy-and 9-bromopentacyclo[4.3.0.02, 5.03, 8.04, 7]nonane (homocubane derivatives) and for the same derivatives of pentacyclo[4.3.0.02, 5.03, 8.04, 7]decane (basketane). The 9-homocubyl and 9-basketyl radicals generated from these precursors were observed by EPR spectroscopy. In spite of their very large strain energies, both radicals rearranged extremely slowly, and unrearranged products were obtained from homolytic reactions in solution at temperatures below 150 °C. At higher temperatures the 9-basketyl radical rearranged by a cascade of three β-scissions, the ultimate product being 1 -(4-cyclobut-2-enyl)cyclohexa-2, 4-diene. The Arrhenius parameters for the rearrangement were found to be log(Ar/s-1) = 13.6, Er= 13.5 kcal mob-1. The 9-homocubyl radical did not rearrange even at 220 °C. An explanation as to why these cage radicals rearrange at least 6 orders of magnitude more slowly than the related cubylcarbinyl radical is presented, and semiempirical SCF-MO calculations are reported.
UR - http://www.scopus.com/inward/record.url?scp=0001162091&partnerID=8YFLogxK
U2 - 10.1021/ja00086a009
DO - 10.1021/ja00086a009
M3 - Article
AN - SCOPUS:0001162091
SN - 0002-7863
VL - 116
SP - 2759
EP - 2766
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 7
ER -