Organic Electrochemistry: Expanding the Scope of Paired Reactions.

Paired electrochemical reactions allow the optimization of both atom and energy economy of oxidation and reduction reactions. While many paired electrochemical reactions take advantage of perfectly matched reactions at the anode and cathode, this matching of substrates is not necessary. In constant current electrolysis, the potential at both electrodes adjusts to the substrates in solution. In principle, any oxidation reaction can be paired with any reduction reaction. Various oxidation reactions conducted on the anodic side of the electrolysis were paired with the generation and use of hydrogen gas at the cathode, showing the generality of the anodic process in a paired electrolysis and how the auxiliary reaction required for the oxidation could be used to generate a substrate for a non-electrolysis reaction. This is combined with variations on the cathodic side of the electrolysis to complete the picture and illustrate how oxidation and reduction reactions can be combined.

Paired Electrochemical Reactions and the On-Site Generation of a Chemical Reagent.

While the majority of reported paired electrochemical reactions involve carefully matched cathodic and anodic reactions, the precise matching of half reactions in an electrolysis cell is not generally necessary. During a constant current electrolysis almost any oxidation and reduction reaction can be paired, and in the presented work we capitalize on this observation by examining the coupling of anodic oxidation reactions with the production of hydrogen gas for use as a reagent in remote, Pd-catalyzed hydrogenation and hydrogenolysis reactions. To this end, an alcohol oxidation, an oxidative condensation, intramolecular anodic olefin coupling reactions, an amide oxidation, and a mediated oxidation were all shown to be compatible with the generation and use of hydrogen gas at the cathode. This pairing of an electrolysis reaction with the production of a chemical reagent or substrate has the potential to greatly expand the use of more energy efficient paired electrochemical reactions.

Triply Hydrogen-Bond-Directed Enantioselective Assembly of Pyrrolobenzo-1,4-diazine Skeletons with Quaternary Stereocenters.

Highly efficient synthesis of optically enriched pyrrolobenzo-1,4-diazines bearing quaternary stereocenters has been realized through the chiral Brønsted acid-catalyzed Pictet-Spengler reaction of 2-(1H-pyrrol-1-yl)anilines and α-ketoamides in good to excellent yields and enantioselectivities. Computational studies suggest an unprecedented phenomenon whereby the chiral phosphoric acid catalyst employs attractive arene C-H⋅⋅⋅N hydrogen bonding to activate the substrate and induce chirality through a triple hydrogen-bonding interaction.