Volume 94 Issue 36 | p. 10 | Concentrates
Issue Date: September 12, 2016

Flow reaction reduces aryl diazonium safety risk

New approach generates potentially explosive intermediate reagents for the Balz-Schiemann reaction without having to handle them directly
Department: Science & Technology
News Channels: Organic SCENE
Keywords: synthesis, safety, Balz–Schiemann, diazonium, aryl fluoride, continuous flow, safety

The Balz-Schiemann reaction is a versatile means for synthesizing aryl fluorides from anilines. But there’s a catch: The procedure involves preparing and isolating intermediate aryl diazonium salts or generating them in situ under batch conditions. Both routes present a safety hazard because diazonium salts have the potential to spontaneously undergo violent decomposition, which has limited the scalability and utility of the reaction. Nathaniel H. Park, Timothy J. Senter, and Stephen L. Buchwald of Massachusetts Institute of Technology have addressed this problem by devising a continuous-flow process to prepare aryl diazonium salts that eliminates the need to handle them directly (Angew. Chem. Int. Ed. 2016, DOI: 10.1002/anie.201606601). The researchers were challenged to find reagents and conditions for their flow reactor that avoid side reactions that sometimes plague the Balz-Schiemann reaction and still lead to the desired aryl diazonium salts. Using the streamlined diazonium preparation shown, they fed the intermediate into a stirred batch reactor for the final dediazotization step to prevent precipitated salt from clogging the reactor channel. The approach enabled the MIT team to quickly and safely produce gram amounts of aryl and heteroaryl fluorides.

 
Chemical & Engineering News
ISSN 0009-2347
Copyright © American Chemical Society

Leave A Comment

*Required to comment