Radical reactions of epoxides. 2. intramolecular competition between cyclopropylmethyl and oxiranylmethyl radical ring‐opening rearrangements

The erythro ‐thioimidazole precursor to the cyclopropyloxiranylmethyl radical has been prepared. Treatment with 7–19 equiv. of triphenyltin hydride at 70°C gave only 3‐cyclopropylprop‐2‐en‐1‐ol, the product of epoxide ring opening. No product in which the cyclopropyl ring had opened was observed. Kinetic analysis allowed the assignment of a lower limit for the rate of oxiranylcarbinyl radical rearrangements of 1 × 10 10 s −1 at this temperature.