Recent Advances in Electro- or Photochemical Driven Transformations via Cleavage of the C–N Bond of Quaternary Ammonium Salts

Abstract Selective functionalization via cleavage of the C–N bond of amines has proven to be challenging partly because of its relatively high bond dissociation energy, even though amines are abundant and readily available. To meet this challenge, many new transformations based on the pre-activation of the C–N bond before the cleavage have been developed. Among them, the conversion of amines into quaternary ammonium salts has certain advantages, such as easy preparation from primary, secondary, or tertiary amines, as well as stable storage and usage. Although transition metal catalysis has been frequently applied for developing new transformations via oxidative addition of the C–N bond of quaternary ammonium salts, recent studies have shown a new dimension by using green electro- or photochemical tools. In this short review, recent advances in electro-, photo-, or photoelectrochemical driven synthetic applications of quaternary ammonium salts have been summarized and discussed. 1 Introduction 2 Electrochemical Driven Transformations 3 Photochemical Driven Transformations 4 Photoelectrochemical Driven Transformations 5 Conclusion and Outlook