To confirm the radical nature of this reaction, a radical clock experiment was conducted (Figure ). Submission of RAEs 34 and 35 to standard conditions led to a mixture of heterocoupled products 36 and 37 resulting from immediate cyclopropane opening and coupling with 5-hexenyl radical either in cyclized or open form, respectively. This is consistent with the common reactivity that RAEs generate alkyl radicals via single electron transfer (SET) followed by rapid fragmentation. Since the coupling reaction barely proceeded when Ni catalyst was omitted (Table , control experiments), the role of the Ni catalyst is presumably either mediating the SET 20,37 or effectively capturing free radicals generated by direct cathodic reduction to facilitate productive reaction pathway. Furthermore, the ratio of 36 and 37 is dependent on Ni catalyst concentration, indicating that cage-escaped radical might be involved for Ni-C bond formation. In addition, such observation is diagnostic for involvement of multiple Ni species in the mechanism, and could exclude possibility of double oxidative addition on a single Ni species (or cage-rebound mechanism). 38-40 Although detailed mechanistic understanding is outside the scope of this initial report, future in-depth kinetic studies may provide further support for this hypothesis.