The Journal of Organic Chemistry
ARTICLE
be uniformly described in terms of a direct hydrogen atom
’ ACKNOWLEDGMENT
abstraction mechanism.
Financial support from the Ministero dell’Istruzione dell’Universitꢀa
e della Ricerca (MIUR) is gratefully acknowledged. We thank Prof.
Lorenzo Stella for the use of a LFP equipment.
’ EXPERIMENTAL SECTION
Materials. Spectroscopic grade acetonitrile and 2,2,4-trimethylpen-
tane (isooctane) were used in the kinetic experiments. Triethylamine
(TEA), tripropylamine (TPA), triallylamine (TAA), triisobutylamine
(TIBA), 1,4-dimethylpiperazine (DMP), 1-azabicyclo[2,2,2]octane
(ABCO), and 1,2,2,6,6-pentamethylpiperidine (PMP) were of the highest
commercial quality available (g99%). TEA, TPA, TAA, TIBA, DMP, and
PMP were further purified prior to use by filtration over neutral
alumina. ABCO was further purified by sublimation. The purity of the
substrates was checked by GC prior to the kinetic experiments and was in all
cases >99.5%.
Dicumyl peroxide was of the highest commercial quality available and
was used as received. Dibenzyl peroxide, dibenzyl peroxide-d4, and
bis(3,5-di-tert-butylbenzyl) peroxide were prepared in small portions by
reaction of KO2 with the pertinent benzylic bromide in dry benzene, in
the presence of 18-crown-6 ether, according to a previously described
procedure.30,47 Details on the synthesis and characterization of the
products are given in the Supporting Information.
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’ ASSOCIATED CONTENT
S
Supporting Information. Details on the syntesis and
b
characterization of the dibenzyl peroxides. Plots of kobs versus
amine concentration for the reactions of CumO•, BnO•,
BnO•-d2, and 3,5-DTBBnO•. This material is available free
(29) A pKa of ꢀ3 has been estimated for the R-CꢀH atoms of the
’ AUTHOR INFORMATION
benzyloxyl radical. See ref 30.
Corresponding Author
*E-mail: bietti@uniroma2.it.
(30) Konya, K. G.; Paul, T.; Lin, S.; Lusztyk, J.; Ingold, K. U. J. Am.
Chem. Soc. 2000, 122, 7518–7527.
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dx.doi.org/10.1021/jo201025j |J. Org. Chem. 2011, 76, 6264–6270