47461-07-4Relevant academic research and scientific papers
The Mechanism of the β-Acyloxyalkyl Radical Rearragement. Part 2: β-Acyloxytetrahydropyranyl Radicals
Beckwith, Athelstan L. J.,Duggan, Peter J.
, p. 1673 - 1680 (2007/10/02)
The rate of rearrangement of the 3-butanoyloxytetrahydropyran-2-yl radical (4) to give the product 5 of 1,2-migration of the acyloxy group has been determined by competition against the reaction of 4 with tributylstannane.The rate constant is larger than that for rearrangement of the acylic radical 18 but less than that for the substituted cholestanyl radical 19.Experiments with 17O- and 18O-labelled substrates indicate that the rearrangement of 4 proceeds with ca. 33percent transposition of the ether and carbonyl oxygen atoms, while there is also a small amount of scrambling in the product 12 formed by direct reduction of 4.The isotope labelling studies and the Arrhenius parameters (log 1> = 12.7, Eact = 58 kJ mol-1) are consistent with the view that the reaction proceeds, at least in part, via dissociation into a tight anion radical-cation pair 22.A pathway via the three-membered transition sturcture 21 might also be involved.
