Electrochemical oxidation synergizing with Brønsted-acid catalysis leads to [4 + 2] annulation for the synthesis of pyrazines

An electrochemical dehydrogenative [4 + 2] annulation for the synthesis of pyrazines has been developed under undivided electrolytic conditions. In this protocol, neither external chemical oxidants nor transition-metal catalysts are needed, and a wide range of substituted pyrazines could be obtained from simple ketones and diamines in high efficiencies. Of note is that this electrolysis could also be extended for the construction of biheteroarenes and large π systems with good yields.