69% yield; tR= 20 min per pass vs. 72 h, 66% yield; Scheme 4B, see S.I. for details). Scale up to 8 mmol increased the reaction time to 24 h (56% yield of 3i) and proved robust and reproducible. CV measurements (see S.I. for details) revealed that the oxidation potential of TPA is +0.99 V vs SCE, while that of arylacetylenes is above +2.1 V vs SCE. Thus, TPA should be initially fully oxidized at the anode but due to the difference in potentials is unlikely to act as a mediator to oxidize the EoAs. We therefore propose that EoAs undergo direct single-electron oxidation at the anode after the complete oxidation of TPA. We then questioned the role of TPA, which, while not necessary for reactivity, is beneficial for an improved yield (Table , entries 1 and 2). CV measurements of TPA-PhCOOH mixtures (Figure ) show that with an increasing molar ratio of benzoic acid, the oxidation current intensity of TPA steadily decreases, whereas the reduction current intensity of PhCOOH increases gradually. This implies that the 'fresh' TPA concentration at the electrode available for oxidation decreases as the PhCOOH loading increases. EPR measurements show the complete disappearance of the strong signal of TPA radical cation 33 after mixing with potassium benzoate (Figure , see S.I. for details), suggesting the single-electron reduction of the TPA radical cation by benzoate anion.