Complete electron economy by pairing electrolysis with hydrogenation

Electrosynthesis provides a method of driving organic reaction chemistry under ambient conditions with electricity. Pairing two reactions together enables the synthesis of two valuable chemicals with no waste product. Here we report the paired electrolysis of 4-methoxybenzyl alcohol to 4-methoxybenzaldehyde with the concomitant formation of 1-hexene from 1-hexyne in an electrochemical cell. These reaction chambers are separated by a dense palladium membrane that reduces protons formed at the anode to hydrogen atoms that can permeate through the palladium foil to hydrogenate 1-hexyne. The palladium membrane enables two reactions to be performed in distinct reaction conditions: hydrogenation in organic solvents and electrochemical oxidation in aqueous electrolyte. The starting materials in both chambers react quantitatively over 5 hours of electrolysis, and selectivities >= 95% can be achieved for 4-methoxybenzaldehyde and 1-hexene with control of reaction conditions. Exquisite control of the reaction kinetics and selectivities of each of the individual reactions is demonstrated.