Electrochemically Enabled Cascade Cyclization Reaction of Aromatic Aldehydes and Pyrazol-5-amines: Synthesis of Bis-pyrazolo[3,4- b :4',3'- e ]pyridines.

A facile method for the synthesis of bis-pyrazolo[3,4- b :4',3'- e ]pyridines from easily available aromatic aldehydes and pyrazol-5-amines was developed via electrochemistry. The reaction proceeded smoothly under metal and external chemical oxidant-free conditions, giving a variety of bis-pyrazolo[3,4- b :4',3'- e ]pyridines in moderate yields.