Allyloxy Radicals are Formed Reversibly from Oxiranylcarbinyl Radicals: A Kinetic Study

Fragmentation of a linoleate-derived γ-hydroperoxy-α,β-unsaturated epoxide to γ-hydroxy- and γ-oxo-alkenals involves a unique pseudo-symmetrical diepoxycarbinyl radical

“…1. The interconversion of allyloxy radicals and epoxy carbinyl radicals[23–25] (the C–O bond formation and cleavage) is one of the fastest known radical reactions[26] (k 1 = 2 × 10 9 s −1 , k −1 = 3.2 × 10 10 s −1 , respectively[27, 28]). C–C bond cleavage of epoxy carbinyl radicals is also known but only if the substrate has radical-stabilizing groups, e.g., phenyl or vinyl.…”

Kinetics of the Oxiranylcarbinyl Radical Rearrangement

“…10 In systems where the oxiranylcarbinyl radical is allowed to compete directly with the well-studied cyclopropylcarbinyl radical rearrangement (k ) 1.0 × 10 8 at 25 °C), 11,12 only products from epoxide fragmentation are observed. [13][14][15] By assuming the reverse reaction (2 f 1) to be relatively slow, an assumption that turns out to be not quite correct, 16 a lower limit for the forward rearrangement was set at 1 × 10 10 s -1 at 70 °C. 14 Our long-standing interest in the synthetic potential of radical-induced epoxide fragmentations [17][18][19][20][21] prompted us to examine the rate of this rearrangement more precisely.…”

Free-Radical Chemistry of Lactones: Fragmentation of β-Lactones. The Beneficial Effect of Catalytic Benzeneselenol on Chain Propagation

“…It is widely appreciated that oxiranylcarbinyl radicals undergo reversible 1,2 ring opening some 2 or more orders of magnitude more rapidly than the corresponding cyclopropylcarbinyl radicals. [3][4][5][6][7] In these reactions, the C-O bond is typically cleaved in preference to the C-C bond (Scheme 1).…”