We followed the reaction of VBX 1a with 2a in THF-d8 by 1 H NMR to investigate the formation of any intermediates and to rationalize the observed influence of the base addition order. When 2a was mixed with tBuOK in an NMR tube, signals of the thiophenolate were immediately observed and the vinylation started instantly when 1a was added. A similar NMR experiment with 1a and 2a in the absence of base showed no interaction between the two, and the reaction only started upon addition of the base. In both cases, no intermediates could be observed. Based on these results, we suggest that the experimental benefit of adding the base last is to suppress the formation of the disulfide byproduct, rather than a mechanistic pathway where initial S-I coordination is followed by deprotonation to give A.