At the same time, control experiments were performed with (3-iodobutyl)benzene (88), a putative intermediate of this reaction (Figure ). First, we tried the standard condition of this reaction using 88 and 4-tert-butylstyrene (2) without electrodes and current, and using Zn dust (10 eq.) and Mn dust (10 eq.) as chemical reductants. Consequently, the desired compound 3 was not obtained at all. In addition, we tried the standard condition of this reaction with (+)C plate / (-)Ni foam and no current flow (0 mA). However, the desired compound 3 was not obtained. Based on these results and the aforementioned control experiments (Figure , entry 1), it can be concluded that the application of electrochemistry is essential for this reaction. A further control experiment was then performed to investigate the effect of FeCl2 in this reaction (Figure , bottom). Sacrificial anodes ((+)Zn plates) were used instead of (+)C plates in the standard reaction conditions. As a result, the desired compound 3 was isolated in 24% yield under the conditions without FeCl2 and IPr ligand. On the other hand, the yield was improved (42% isolated yield) under the condition with FeCl2 and IPr ligand. These experimental results indicated that the FeCl2 and IPr ligands are crucial in this reaction system. It is interesting to note that in the Giese reaction of 4-phenyl-2-butanol (1) and 4-tert-butylstyrene (2), the isolated yield under standard conditions was 60% (Figure ). This yield is higher than that of (3iodobutyl)benzene (88) in a sacrificial anode ((+)Zn plate) (Figure 2B, bottom). This is probably due to the fact that this reaction does not use alkyl halide as a starting material, but alcohol as a starting material, which allows the gradual formation of alkyl halide in the reaction system and keeps the concentration of radicals at a reasonable level. From these experimental results, it can be concluded that FeCl2 is essential for this reaction. In addition, the importance of keeping the radical concentration in the reaction system at a reasonable value is evident.