Based on the above, a plausible mechanistic rationale (Figure ) starts with the initial electrochemical oxidation of TPA to furnish the TPA radical cation at a relatively mild potential (1.0 V vs SCE). In turn, the reduction of benzoic acid leads to hydrogen gas evolution and the formation of a benzoate anion (BA¯), which creates a charge transfer complex A with the TPA radical cation. In the productive phase of the reaction, EoA 1 eventually undergoes a single electron oxidation at the anode to generate a vinyl radical cation intermediate I. Subsequent nucleophilic trapping of I by nitrile 2 gives rise to intermediate II, which undergoes cycloaddition preferentially with EnoA, generating vinyl radical intermediate III/IV. Single electron transfer from the charge transfer complex A followed by protonation provides the protonated cross-annulated product 4-H + with concurrent formation of phenylcarboxylic radical (BA˙). Reduction of the latter at the cathode regenerates a phenylcarboxylate anion (BA¯), which recombines with the TPA radical cation to A ready for the next cycle. Intermediate IV also can be directly reduced at the cathode, which we assume is less effective than SET by complex A.