Electrochemical synthesis of tetrahydrobenzo[b]pyran derivatives in deep eutectic solvents

The current work reported the first synthesis of 4H-pyran derivatives via one pot reaction of dimedone, malononitrile and aromatic aldehydes under electrochemical (EC) synthesis conditions in deep eutectic sol-vents (DES). The effects of different experimental factors like; solvent, electrodes, supporting electrolytes, tem-perature and reaction time were studied to optimize the reaction conditions in order to maximize the products yield. The reaction proceeded completely using different substituted aldehydes except for hydroxybenzaldehy-des where oxidation seems to hinder the formation of the target reaction product. Combining EC and DES afforded the pyran derivatives in high yields within short reaction times and in highly pure forms. Moreover, the use of DES eliminated the need for supporting electrolyte. The DES have been recycled two times without a significant loss in the catalytic activity. The procedure was highly efficient, catalyst-free and eco-friendly as evident from the calculations of the green chemistry metrics.

Automated summary

This study reported the first synthesis of 4H-pyran derivatives using electrochemical synthesis conditions and deep eutectic solvents in a one pot reaction. By optimizing the reaction conditions, high yields of pure pyran derivatives could be obtained in a short amount of time. The use of deep eutectic solvents also eliminated the need for a supporting electrolyte, improving the sustainability of the catalyst.