A general electrochemical strategy for the Sandmeyer reaction

Area of Science:

• Organic Chemistry
• Electrochemistry
• Synthetic Methodology

Background:

• The Sandmeyer reaction is a crucial method for synthesizing aryl halides.
• Traditional Sandmeyer reactions often require stoichiometric amounts of metal catalysts and harsh reagents.
• Developing greener and more efficient synthetic routes is essential in modern organic chemistry.

Purpose of the Study:

• To develop a general electrochemical strategy for the Sandmeyer reaction.
• To utilize electricity as a clean driving force for halogenation.
• To enable a one-pot synthesis of aryl halides from readily available anilines.

Main Methods:

• Electrochemical halogenation of aryl diazonium salts using various halogen sources (NBS, CBrCl3, CH2I2, CCl4, LiCl, NaBr).
• One-pot synthesis starting from anilines.
• Multigram scale synthesis using graphite electrodes.
• Mechanistic investigations including radical clock, radical scavenger studies, cyclic voltammetry, and in situ electron paramagnetic resonance (EPR) analysis.

Main Results:

• A general and efficient electrochemical protocol for the Sandmeyer reaction was established.
• Successful halogenation of aryl diazonium salts was achieved using inexpensive halogen sources.
• The reaction proceeded effectively in a one-pot manner from anilines.
• The method was validated through multigram scale synthesis of aryl halides.
• Detailed mechanistic insights were obtained through various analytical techniques.

Conclusions:

• The developed electrochemical strategy offers a sustainable and practical alternative for aryl halide synthesis.
• This method provides a versatile platform for the Sandmeyer reaction, applicable to a wide range of substrates.
• The use of electricity and inexpensive graphite electrodes highlights the potential for greener chemical manufacturing.